References of "Degré, Aurore"
     in
Bookmark and Share    
Full Text
See detailUtilisation de la CNOSW en tant que carte d'occupation du sol dans le modèle EPICgrid
Sohier, Catherine ULg; Degre, Aurore ULg

Poster (2010, October 20)

Le modèle EPICgrid est un modèle hydrologique distribué de résolution 1km² couvrant toute la Wallonie. Il a été développé par Gx-ABT afin d’évaluer les flux d’eau, de nutriments et de sédiments vers les ... [more ▼]

Le modèle EPICgrid est un modèle hydrologique distribué de résolution 1km² couvrant toute la Wallonie. Il a été développé par Gx-ABT afin d’évaluer les flux d’eau, de nutriments et de sédiments vers les eaux de surface et vers les eaux souterraines. Il permet, entre autres, de tester l’impact de scénarios de gestion des nutriments sur la qualité des eaux en Région wallonne ainsi que des rapportages à différentes échelles dont les masses d’eau de surface. Le modèle requiert parmi ses données d’entrée une cartographie de l’occupation du sol. Dans un premier temps, la carte d'occupation des sols utilisée était issue du projet CARHY (Laime et Dautrebande, 1995) et reposait sur l'analyse d'images satellitaires Landsat pour refléter l’occupation du sol des années '90. En 2009, la CNOSW a été implémentée dans le modèle pour affiner spatialement et mettre à jour cette donnée en vue de simulations hydrologiques prospectives. Pour ce faire, les différentes classes de la CNOSW (niveau 5) ont été complétées au niveau des zones non cadastrées afin d’obtenir une couverture continue, hydrologiquement valide, de toute la Wallonie. Les classes ont ensuite été regroupées en classes hydrologiques d’occupation du sol (7 classes). La comparaison des cartes d’occupation du sol CARHY et issue de la CNOSW montre une répartition en classes similaire au niveau régional. Néanmoins, au niveau local, les différences marquées peuvent être constatées. Les zones urbaines sont également mieux représentées par la CNOSW. L’introduction de la CNOSW dans le modèle EPICgrid en apportant une spatialisation plus précise des occupations du sol a permis d’affiner les résultats du modèle et d’ouvrir de nouvelles pistes de développement telles que la représentation dans le modèle hydrologique du fonctionnement des bandes enherbées riveraines et inter-parcellaires. [less ▲]

Detailed reference viewed: 27 (7 ULg)
Full Text
See detailNouveaux outils de gestion intégrée sol érosion ruissellement GISER
Degre, Aurore ULg; Colard, François ULg

Conference given outside the academic context (2010)

L'exposé présente une synthèse des développements d'arctoolboxes dédiées à la gestion spatiale de la problématique du ruissellement, de l'érosion et du dépôt des sédiments à l'échelle des bassins versants ... [more ▼]

L'exposé présente une synthèse des développements d'arctoolboxes dédiées à la gestion spatiale de la problématique du ruissellement, de l'érosion et du dépôt des sédiments à l'échelle des bassins versants agricoles. [less ▲]

Detailed reference viewed: 50 (22 ULg)
Full Text
Peer Reviewed
See detailHydrologic modelling and dendrochronology as tool of site-species adequation assessment in a changing climate context
Sohier, Catherine ULg; Debruxelles, Jérôme ULg; Brusten, Thomas ULg et al

Poster (2010, September 21)

A hydrologic model is related to dendrochronological measurements performed in a 52 years old Spruce stand. The site is situated on a hillside with shallow and acid brown soil in the ecoregion of Ardenne ... [more ▼]

A hydrologic model is related to dendrochronological measurements performed in a 52 years old Spruce stand. The site is situated on a hillside with shallow and acid brown soil in the ecoregion of Ardenne (Wallonia, Southern Belgium). Hydrologic modelling The hydrologic simulation runs from 1971 to 2005 at daily time step. The model is based on an EPIC code, adapted to the site concerning soil reservoirs depth, characteristic water contents, root profile and water uptake. Weather data come from the Royal Meteorological Institute. Outputs from the model are real evapotranspiration, surface runoff; interflows, deep percolation and soil moisture at daily time step. Dendrochronological study Tree ring thickness is measured on 24 core samples extracted from 12 dominant trees of the stand. Annual increments are standardised by the ARIMA function in order to produce the annual deviation of ring thickness. Means of annual deviation for the 12 trees are then related to annual soil drought intensities. Results Years 1976 and 1996 are emphasised by both the modelling outputs and the dendrochronological measurements as very dry. Model shows a severe drought and tree ring shows a very low growth. Years like 1990, 1992, 1994 and 2004 shows a less severe drought event but a drought that occurs in June-July, which seems to penalize spruce’s growth. On the other hand, years 1981 and 1998 show an important growth and a high value of mean soil moisture during June and July. The poster will show how the time evolution of the ARIMA index is related to some meaningful hydrologic indexes. These considerations will allow us to progress towards forecasting forest trees reaction to climate events and change. With this in mind, we will use a climate scenario build up in the frame of the AMICE interreg project. [less ▲]

Detailed reference viewed: 100 (51 ULg)
Full Text
See detailAnalysis of climate change, high-flows and low-flows scenarios on the Meuse basin: WP1 report - Action 3
Drogue, G.; Fournier, M.; Bauwens, Alexandra ULg et al

Report (2010)

Detailed reference viewed: 90 (44 ULg)
Full Text
See detailInondations en aval : quelles aides peuvent fournir les zones humides en amont?
Degre, Aurore ULg; Sohier, Catherine ULg

Conference given outside the academic context (2010)

Detailed reference viewed: 21 (9 ULg)
Full Text
Peer Reviewed
See detailComparison of agricultural soils' structure depending on tillage system using X-ray microtomography
Beckers, Eléonore ULg; Ly, Sarann ULg; Léonard, Angélique ULg et al

in Geophysical Research Abstracts (2010, May), 12

This study aims at characterizing agricultural soils’ structure depending on the tillage system: conventional tillage or conservational tillage. Tillage reduction is an increasing practice, but the micro ... [more ▼]

This study aims at characterizing agricultural soils’ structure depending on the tillage system: conventional tillage or conservational tillage. Tillage reduction is an increasing practice, but the micro-structural effects on soils and on their hydrodynamic parameters are still not well described. Recent research shows non-converging results. Our point is to highlight fundamental differences in structure through characterization of soils porosity’s parameters using X-ray microtomography measurements coupled to image analysis. This attempt is in line with a more integrated experiment of which the aim is to quantify the effects of tillage intensity on lateral flow production, and finally on global water balance. Parameters’ measurements consist in a combined approach, based on two different space-time scales of exploration: fundamental scale, with soil sampling campaign for microtomography analysis, and field scale, with continuous flow measurements (plots’ dimensions: 18*28 m). For their part, parameters for water balance determination (precipitation, evapotranspiration…) are monitored on the field. All of these measurements have the main objective of hydrological modeling enhancement by taking into account a better lateral flow description. Discussion in this paper will focus on the first results obtained by X-ray microtomography measurements. Our experiment takes place in Gentinnes (Walloon Brabant, Belgium), on a field organized in a split-plot scheme. Since 2004, plots have been cultivated in conventional tillage or in reduced tillage. The latter consists in sowing after stubble ploughing of about 10cm. The crop rotation is sugar beet followed by winter wheat. The soil is mainly composed of silt loam. Soils samples, with a 3 cm diameter and a 5 cm height, were removed from the upper layer (Ap horizon) for both management practices. Samples are scanned by X-ray microtomography using a Skyscan-1172 high-resolution desk-top micro-CT system (Skyscan, Kontich, Belgium). The cone beam source operated at 100 kV, using an aluminium filter. The detector configuration, i.e. 1048×2000 pixels 16-bit X-ray camera, and the distance source-object-camera were adjusted to produce images with a pixel size of 17 µm. This resolution allows us to visualize both meso- and macro- porosity. In this study, half the samples were placed under a 15000 kPa pressure (corresponding pressure for the wilting point) in Richards’ apparatus in order to empty the meso- and macro-porosity. To determine a priori the class of porosity for the samples, relations between water retention and pressure head can be plotted using this apparatus. Scanning results consist in 2D images. The 2D images are recombined to form 3D structure. Then the pore network can be analyzed through useful factors like size distribution, shape, connectivity, orientation, tortuosity etc. [less ▲]

Detailed reference viewed: 104 (53 ULg)
Full Text
Peer Reviewed
See detailSpatial interpolation of daily rainfall in Ourthe and Ambleve Basins, Belgium
Ly, Sarann ULg; Sohier, Catherine ULg; Charles, Catherine ULg et al

in Geophysical Research Abstracts (2010, May)

Spatial interpolation of precipitation data is of great importance for hydrological modelling. The methods of geostatistics (krigings) become more popular to make spatial interpolation from point ... [more ▼]

Spatial interpolation of precipitation data is of great importance for hydrological modelling. The methods of geostatistics (krigings) become more popular to make spatial interpolation from point measurement to distributed hydrological models. However, most of existing geostatistic algorithms are available only for single-moment data. The first step of Kriging computation is the semi-variogramme modelling which usually uses only one variogramme model for all-day data. The objective of this paper is to review the implementation of an algorithm of spatial interpolation methods for daily rainfall and to compare the results of geostatistic and deterministic approaches. In this study, we will use daily rainfall data from 70 rain gauges in the hilly landscape of Ourthe and Ambleve Basins in Belgium (2751 km2). This area lies between 35 and 690 m in elevation and consists of river networks which are the tributaries of the Meuse River. The proposed algorithm will use the method of Cressie’s Approximate Weighted Least Squares to fit among sevens semi-variogramme models (logarithmic, power, exponential, Gaussian, rational quadratic, spherical and penta-spherical) to daily sample semi-variogrammes. These seven models are computed on a daily basis. Firstly, one model is chosen by considering the minimum of least squares coefficient. Secondly, if the chosen model gives negative interpolated values, other models will be chosen again until the result become positive. Cross validation will be used to compare the interpolation performance of geostatistic to deterministic methods usually known as Thiessen polygon and Inverse DistanceWeighting (IDW). [less ▲]

Detailed reference viewed: 80 (27 ULg)
Full Text
Peer Reviewed
See detailIntegrated Methodology of Instream Flow Assessment : Study of a Belgian River, the Crupet
Hirtt, Laura; Degre, Aurore ULg

in AgroEnviron2010: VII international symposium Environmental sustainability of Agricultural management systems in an ever changing world (2010, May)

Pumping stations and dams generate modifications of rivers’ state flow. In this work, we propose to implement and compare the results of three instream flow assessments. We are studying a Belgian river ... [more ▼]

Pumping stations and dams generate modifications of rivers’ state flow. In this work, we propose to implement and compare the results of three instream flow assessments. We are studying a Belgian river called Crupet, which has some pumping stations on its catchment. The Crupet medial flow is 0.56 m3/s at the point of discharge of the catchment. The three methods are : the Range of Variability Approach, the Instream Flow Incremental Methodology and the Wetted Perimeter Method. The aim of the first method is to find an instream flow so that the river conserves as much as possible its natural behaviour after pumping. This method is usually based on twenty years of flow data, before and after the construction of the pumping stations. In our case, the data were not available, especially because there are no stage gauging stations. So we had to generate hydrologic data based on some approximations and hypotheses (estimation of the quantity of water pumped on the catchment, method of regionalisation). Next, we used the IHA software to analyse the alteration of thirty-three hydrologic parameters, and we formulated an equation that calculates how much water could be pumped to minimize the alteration of the parameters. The second method is based on hydrological, morphological, and biological (fish habitat) data to assess the minimum flow in a river at low water. The third method, the Wetted Perimeter Method, is used to find the minimum flow knowing the morphology of the transect (relation between wetted perimeter and flow). For the last two methods, we found the minimum flow for the studied section being equal to 1.5 m3/s. The RVA methodology recommends, however, a higher minimum flow and imposes to reduce the pumping, at least if all our hypotheses are correct. [less ▲]

Detailed reference viewed: 67 (14 ULg)
Full Text
Peer Reviewed
See detailHow Climate Change Could Affect The Hydrology In Walloon Region ?
Bauwens, Alexandra ULg; Sohier, Catherine ULg; Degre, Aurore ULg

Poster (2010, April 22)

Research on climate change and its impacts on hydrology are increasingly important nowadays. AMICE project focuses on the adaptation of the Meuse to the impacts of climate change. On this study, we focus ... [more ▼]

Research on climate change and its impacts on hydrology are increasingly important nowadays. AMICE project focuses on the adaptation of the Meuse to the impacts of climate change. On this study, we focus on the Walloon tributaries of the Meuse river, and more specifically on the Vesdre and the Lesse sub-catchments. Climate change scenarios are outputs of the CCI-HYDR Perturbation Tool for time slice 2020-2050 and 2070-2100. This tool allows us to build climate change time series and to use it as input of our hydrological models. The most pessimistic and the most optimistic scenarios are selected. The hydrological model used is called EPICGrid and it is a physically based distributed model at catchment scale. EPICGrid used the perturbed meteorological data to provide hydrograms for the different scenarios and time slice for the Vesdre and the Lesse sub-catchments. It appears that for the Vesdre daily discharge with a return period of 100 years (Qd100) could varies between -3% and +27% when the mean annual 7-day Minimum flow with a return period of 50 years (MAM750) varies between -37% and +16% for 2070-2100. For the Lesse, Qd100 varies between -30% and +50% when MAM750 varies between -21% and +28% for 2070-2100. The broad range of discharge variations reflects the broad range of meteorological variation. These results will be used further in the AMICE project to build an adaptation strategy. [less ▲]

Detailed reference viewed: 58 (16 ULg)
Full Text
Peer Reviewed
See detailHydrological modelling of the EU Nitrates Directive Actions Programme: new developments in the Walloon Region (Belgium)
Sohier, Catherine ULg; Dautrebande, Sylvia; Degre, Aurore ULg

Poster (2010, April)

Wallonia (Southern Region of Belgium) implemented the Nitrates Directive through a first actions plan in 2002 followed by a second action plan in 2007. It designated vulnerable zones and introduced ... [more ▼]

Wallonia (Southern Region of Belgium) implemented the Nitrates Directive through a first actions plan in 2002 followed by a second action plan in 2007. It designated vulnerable zones and introduced various mandatory practices in order to reduce the nitrate contamination risk. At the same time, the government decided to fund non mandatory practices focused on agro-environment. Some of these (like buffer strips) should also be useful in nutrient mitigation. In order to assess the global effectiveness of all the mitigation practices, we have been developing a hydrological model spatially distributed using a 1km² grid cell on the whole Region (16 900 km²). The EPICgrid model represents the root zone and the vadose zone. In Wallonia, groundwater tables are more than 30 m deep in 8% of the territory. It is therefore of major importance to fill the gap between the root zone and the groundwater bodies. It allows us to assess the nitrate transfer time and forecast the mitigation measures’ effect in time, space and amplitude. On the ground, runoff and sediment yield are modelled at the small watershed scale in order to assess buffer strips’ effect on sediment deposition and its consequences on N and P mitigation. The poster will explain the more recent results that consist in forecasting action plans’ effect until 2015 (on both surface water bodies and groundwater bodies) and modelling of the current buffer strips’ effect. [less ▲]

Detailed reference viewed: 29 (4 ULg)
Peer Reviewed
See detailRepresenting Grassed Buffer Strips’ Hydrology in a Regional Scale Model
Sohier, Catherine ULg; Degre, Aurore ULg

Conference (2010, April)

In Walloon Region (Belgium), like in many other European countries, riparian buffer strips appear to become one of the most approved nutrient mitigation measures. Within the frame of the water framework ... [more ▼]

In Walloon Region (Belgium), like in many other European countries, riparian buffer strips appear to become one of the most approved nutrient mitigation measures. Within the frame of the water framework directive, policy makers need nutrient mitigation forecasting at the scale of the surface water bodies (from 3 to 426 km² in Wallonia). It induces that the hydrological models have to deal with different designs of the buffers themselves and of their catchment areas. Up to date, most of the studies focused on sediment deposition at field scale. They concluded that the grassed strips can be very effective; nevertheless, the measured effects are still very variable. More often, the way the runoff water passed through the buffer strip (diffused or concentrated flow) is not considered. We adapted our regional hydrological model (physically based, spatially distributed over the 17.000 km² Walloon region (Sohier et al., 2009)) by developing a new “buffer strip subroutine” that identifies automatically the catchment area of all the buffer strips. This is done using a 10 m resolution DTM. The catchment area is then subdivided into an “area of flow concentration” that leads the water to pass through the buffer strip on a very small portion of it and into an “area of diffuse flow” that leads the water to pass through the buffer strip using its whole length. The daily fluxes of water, nutrient and sediments that pass through the buffer are calculated by the model using our dynamic geodatabases (soil, DTM, weather, land use, agricultural practices). Depending on whether the flow is diffused or concentrated the water depth can vary to a large extent; so does the deposition ratio (algorithm adapted from Deletic, 2001). The buffer itself is modelled as grassland without direct fertilisation. Water and nutrient coming from the watershed can be used by the grass, water can infiltrate, evaporate or runoff and denitrification can occur when the soil is saturated. The oral presentation will show our results at the water body level for different buffer strip scenarios considering sediments and nitrate reduction in surface water. [less ▲]

Detailed reference viewed: 34 (9 ULg)
Full Text
Peer Reviewed
See detailApproach of regionalization of low flow of the Walloon Region
Gailliez, Sébastien; Degre, Aurore ULg

Poster (2010, April)

The walloon part of the Meuse’s watershed represents 12283 km² and 17694 km of river. The anthropogenic pressure is important (population density is more or less 200 inhabitants/km²). In low flow period ... [more ▼]

The walloon part of the Meuse’s watershed represents 12283 km² and 17694 km of river. The anthropogenic pressure is important (population density is more or less 200 inhabitants/km²). In low flow period, water scarcity can touch both the water users (producer of drinking water and hydropower, tourism and pleasure activities and kayaking) and the river itself affecting the ‘good environmental state’ (context of Water Framework Directive 2000/60/CE). The operational management of rivers during low flow periods needs a deep knowledge of this drought phenomenon including an analysis of low flow severity and its occurrence probability. It also needs the computation of low flow discharge at any point of a river based on available hydrologic variables. The aim of this study is the low flows’ regionalization in the Walloon Region. First of all, the time series of flow data are filled in and validated. The quality is then controlled. The different tests are the determination of the minimum year requirement for a monitoring site, homogeneity tests, verification of presence or absence of summer alga and the proportion of extrapolation of the discharge rating curve Secondly, homogeneous regions will be defined and regression equations will be build. These equations will establish the relation between low flow and physical parameters (watershed area, pedology, slope), climate ones and/or ground water ones. The regression model will permit the computation of low flow discharge at any point of an ungauged river. [less ▲]

Detailed reference viewed: 28 (9 ULg)
Full Text
Peer Reviewed
See detailEvaluation of climate changes impact on the hydrological behaviour of the peaty mediums - Application to the Haute Lesse-Ourthe area (Belgium).
Sohier, Catherine ULg; Dautrebande, Sylvia; Degre, Aurore ULg

Poster (2010, April)

The peaty and wet mediums have a very important role to play in term of biodiversity conservation, hydrologic pattern regulation, fauna habitat and landscape value. In the Haute Lesse – Ourthe catchments ... [more ▼]

The peaty and wet mediums have a very important role to play in term of biodiversity conservation, hydrologic pattern regulation, fauna habitat and landscape value. In the Haute Lesse – Ourthe catchments (Saint-Hubert), numbers of these mediums were strongly modified by a drainage network. This drainage network was implemented to permit a forestry production focussed on the Spruce. It has severely disturbed the hydrological cycle. The study consists in modelling the impacts of restoration practices carried out notably within the framework of the LIFE European project on the hydrological behaviour of the peat bog. Then we modelled the effect of climate change. Physical properties and retention curve of peaty materials were characterized on the basis of undisturbed samples using the Richards’apparatus. Calculations were carried out with the hydrological model EPICgrid (GxABT). The model was initially validated on several reference catchments of the study zone. It was then applied at local scale for various peaty mediums (peat type, drainage characteristics, vegetation type) and for current and future climatic conditions. A regional simulation was finally carried out in order to evaluate the impacts of peat bogs restoration measures at catchment scale. Simulations highlighted the differences in physical and hydrous properties of the different peat types (“true” peat and “degraded” peat). Local and regional impacts of peat bogs restoration on their hydrological behaviour have been evaluated. Eventually, simulations allowed us to evaluate climate change’s impact on the hydrological behaviour of the peaty mediums. The model showed notably that future climatic conditions could generate severe droughts which can become critical in some situations. [less ▲]

Detailed reference viewed: 14 (3 ULg)
Full Text
See detailEcoulement de l'eau dans les sols
Degre, Aurore ULg

Learning material (2010)

Detailed reference viewed: 42 (10 ULg)
Full Text
See detailAssessing structure potential in soil and water conservation: monitoring top soil hydrology from micro to field scale.
Kummert, Nora ULg; Beckers, Eléonore ULg; Roisin, Christian et al

in Wollesen de Jonge, Lis; Moldrup, Per; Lindblad Vendelboe, Anders (Eds.) 1st international conference and exploratory workshop on soil architecture and physico-chemical functions "CESAR" (2010)

Soil structure is a key parameter influencing erosion and water transfers. This paper describes an experiment that covers different aspects of soil structure. Three tillage systems are tested: reduced ... [more ▼]

Soil structure is a key parameter influencing erosion and water transfers. This paper describes an experiment that covers different aspects of soil structure. Three tillage systems are tested: reduced tillage, and two ploughing systems. At micro-scale, analyses are tomography which study images to determine porosity characteristics (connectivity, size, number…) and pF curves where total available water and effective porosity are deducted. At field scale, soil losses and runoff are collected and measured after rainfall simulation on plots for the different tillage systems. The comparison of the results for both scales shows the links between phenomenons at those scales. [less ▲]

Detailed reference viewed: 44 (19 ULg)
Full Text
Peer Reviewed
See detailModelling the effects of the current policy measures in agriculture: an unique model from field to regional scale in Walloon region of Belgium
Sohier, Catherine ULg; Degre, Aurore ULg

in Environmental Science & Policy (2010), 13(2010), 754-765

Diffuse nutrient loss from agriculture into the soil, groundwater and surface water affects their quality. Different policies are in force throughout the European Union aiming for their limitation. They ... [more ▼]

Diffuse nutrient loss from agriculture into the soil, groundwater and surface water affects their quality. Different policies are in force throughout the European Union aiming for their limitation. They were implemented through action plans on a regional scale. Hydrological modelling can be a powerful method for efficiently evaluating their effectiveness. In order to be useful whatever the action and for every reporting unit (whole Region, water bodies, nitrate vulnerable zones, fields...) the model must be physically based, it must simulate water and nutrient fluxes in the root zone and the vadose zone as well as being geographically flexible. This paper presents such a model and its application in the context of Wallonia (Southern part of Belgium). It also presents a calculation of what water and nutrient flows could be under a given climatic scenario until 2015. In Belgium, water quality depends upon Regions. Wallonia implemented the European Nitrate Directive through two action plans the first in 2002 and the second in 2007. These actions plans were modelled and compared to a scenario without any modification in the farmers’ practices. The modelling showed the need for two indicators: nitrate concentration under the root zone as fast indicator of the actions’ efficiency and transfer time from surface to groundwater table. The first action plan hardly modified farmers’ field practices and consequently it did not impact water quality. The second action plan had more impact (reduction up to 10 mg/l NO3 under the root zone). It was mainly due to catch crop introduction in the nitrate vulnerable zone, if they are followed by a reduction of the mineral fertilisation (not mandatory). Our results show that new actions are necessary. We show where and to what extent they have to be implemented. Nevertheless, the greatest variation in nitrate leaching from the root zone seems to be dependent on the weather, more than the action plans. Particularly the rainy period between 1998 and 2002 had a huge impact on nitrogen flows. Our hydrological modelling is showed to be a powerful tool of nitrogen management in a still uncertain climatic evolution context. Finally, we showed that patience and perseverance will be necessary to reach the targets of the WFD in the Walloon context. The map of transfer time shows that 8% of the groundwater bodies need over 15 years to be impacted by mitigation measures. [less ▲]

Detailed reference viewed: 55 (23 ULg)
Full Text
See detailMesure et spatialisation des précipitations
Degre, Aurore ULg; Hirtt, Laura ULg; Beckers, Eléonore ULg

Learning material (2010)

Detailed reference viewed: 64 (13 ULg)
Full Text
See detailHydrologie générale : le bassin versant
Degre, Aurore ULg; Hirtt, Laura ULg; Beckers, Eléonore ULg

Learning material (2010)

Detailed reference viewed: 51 (22 ULg)
Full Text
Peer Reviewed
See detailHydrological modeling of the EU Nitrates Directive Actions Programme:
Sohier, Catherine ULg; Dautrebande, Sylvia; Degre, Aurore ULg

Poster (2009, December 11)

Detailed reference viewed: 27 (7 ULg)