1. G. Leitmann Extremal rocket trajectories in position and time dependent force fields, Am. Astronaut. Soc. 7th Ann. Meeting, Dallas, Preprint 61–30 1961
2. On the equation of rocket motion;Leitmann;J. Brit. Interplanet. Soc.,1947
3. R.T. Stancil & L.J. Kulakowsky Rocket boost vehicle mission optimizations, Am. Rocket Soc. 15th Ann. Meeting, Washington, D. C., Preprint 1449–60 1960
4. F.A. Valentine The problem of Lagrange with differential inequalities as added side conditions, Dissertation, Department of Mathematics, Univ. of Chicago, Chicago, Illinois, 1937
5. Lectures on the Calculus of Variations.;Bliss,1946