1. The high order maximal principle;Krener,1974
2. Controllability of nonlinear systems;Sussmann;J. Differential Equations,1972
3. On the nonlinear control problem with control appearing linearly;Hermes;SIAM J. Control,1963
4. High order necessary conditions for optimality;Gabasov;SIAM J. Control,1972
5. On necessary and sufficient conditions for local controllability along a reference trajectory;Hermes,1974