1. Bisplinghoff, R. L. and Ashley, H., Principles of Aeroelasticity, Wiley, New York, 1962, pp.385-388.
2. Optimization of structures to satisfy flutter requirements.
3. Van de Vooren, A. I., Theory and Practice of Flutter Calculations for Systems with Many Degrees of Freedom, Doctoral Thesis Published by E. Ijdo N. V., Leyden,Holland, 1952.