Feeny B.F., Liang Y. Interpreting proper orthogonal modes of randomly excited vibration systems. Journal of Sound and Vibration. 265:2003;953-966.
Feeny B.F., Kappagantu R. On the physical interpretation of proper orthogonal modes in vibrations. Journal of Sound and Vibration. 211:1998;607-616.
Feeny B.F. On the proper orthogonal modes and normal modes of continuous vibration systems. Journal of Vibration and Acoustics. 124:2002;157-160.
Kerschen G., Golinval J.C. Physical interpretation of the proper orthogonal modes using the singular value decomposition. Journal of Sound and Vibration. 249:2002;849-865.
Lin W.Z., Lee K.H., Lu P., Lim S.P., Liang Y.C. The relationship between eigenfunctions of Karhunen-Loève decomposition and the modes of distributed parameter vibration system. Journal of Sound and Vibration. 252:2002;527-544.
North G.R. Empirical orthogonal functions and normal modes. Journal of the Atmospheric Sciences. 41:1984;879-887.