1. Lagrange, J. L., Oeuvres deLagrange, Vol. 5, Gauthier Villars, Paris, 1870, p. 97.
2. DeBra, D. B. and Delp, R. H. "Rigid Body Attitude Stability and Natural Frequencies in a Circular Orbit/' Journal of the Astronautical Sciences, Vol.8, 1961, pp.14-17.