1. Greenberg M. D. “Singular Points ” Foundations of Applied Mathematics Prentice‐Hall Inc. Englewood Cliffs N.J. 1978.
2. Effects of Foundation Tipping on Dynamic Response
3. Nayfeh A. H. “Variation of Parameters and Methods of Averaging ” Perturbation Methods Wiley‐Interscience New York N.Y. 1973.
4. Nayfeh A. H. and Mook D. T. “Forced Oscillations of Systems Having a Single Degree of Freedom ” Nonlinear Oscillations Wiley‐Interscience New York N.Y. 1979.
5. Seismic Design Spectra for Nuclear Power Plants