1. Alishenas, T., Dahlquist, G.: Personal communication. KTH Stockholm 1989
2. Arnold, V.I.: Mathematical methods of classical mechanics. Berlin Heidelberg New York: Springer 1978
3. Brenan, K.B., Campbell, S.L., Petzold, L.R.: Numerical solution of initial value problems in ordinary differential-algebraic equations. New York Amsterdam London: North Holland 1989
4. Campbell, S.L., Meyer, C.D.: Generalized inverses of linear transformations. Montreal: Pitman 1979
5. Campbell, S.L., Leimkuhler, B.: Differentiation of constraints in differential-algebraic equations. Mech. Struct. Machines (to appear)