1. Bishlinghoff, R. L., Ashley, H., and Halfman, R. L., Aeroelasticity ( Addison-Wesley Publishing Company, Inc., Cambridge, Mass. 1955), Chap. II, pp.15-32.
2. Fimg, Y. C., An Introduction to the Theory of Aeroelasticity (John Wiley and Sons, Inc., New York, 1955), Chap. I, pp.19-27.