1. Lawden, D. F.,Optimal Powered Arcs in an Inverse Square Law Field, ARS Journal, Vol. 31, p. 566, 1961.
2. Lawden, D. F.,Optimal Intermediate-Thrust Arcs in a Gravity Field, Astronautica Acta, Vol. 8, p. 106, 1962.
3. Kelley, H. J.,Singular Extremals in Lawden's Problem of Optimal Rocket Flight, AIAA Journal, Vol. 1, p. 1578, 1963.
4. Kelley, H. J., Kopp, R. E., andMoyer, A. G.,Singular Extremals, Optimization Theory and Applications, Edited by G. Leitmann, Academic Press, New York, New York, 1966.
5. Marchal, C.,Généralisation Tridimensionnelle et Étude de l'Optimalité des Arcs a Poussée Intermédiaire de Lawden (Dans un Champ Newtonian), La Recherche Aerospatiale, No. 123, 1968.