[1] Melod Michel hanna, "An Efficient Mode Superposition method for the Numerical Dynamic Analysis of Bilinear Systems",Dissertation of Ph. D, University of California, Irvine, 1989
[2] Wildson, E, L., and Leger, P., "Modal Summation methods for Structural Dynamic computations," Earthquake Engineering and Structral Dynamics, Vol. 16, 23 ~ 27, 1988