1. Integrability and the variational formulation of non-conservative mechanical systems
2. C. Lanczos, The Variational Principles of Mechanics, 4th edition, republication of a 1970 edition that was published by the University of Toronto Press as vol. 4 of their series Mathematical Expositions; the first edition was published in 1949 (Dover, New York, 1986).
3. J.I. Neimark and N.A. Fufaev, Dynamics of non-holonomic systems, Vol. 23, Translations of Mathematical Monographs series (this is a translation by Julian Barbour of the Russian version, Moscow, 1967) (American Mathematical Society, Providence, R.I., 1972).
4. D.H. Sattinger and O.L. Weaver, Lie Groups and Algebras, with Applications to Physics, Geometry, and Mechanics (Springer, Berlin, 1986).
5. F. Warner, Differentiable Manifolds and Lie Groups (Scott Foresman, Glenview, IL, 1971).