1. Translations of Mathematical Monographs;L. E. El'sgol'c,1964
2. Hughes, D. K.,Variational and Optimal Control Problems with Delayed Argument, Journal of Optimization Theory and Applications, Vol. 2, pp. 1?14, 1968.
3. Sabbagh, L. D.,Variational Problems with Lags, Journal of Optimization Theory and Applications, Vol. 3, pp. 34?51, 1969.
4. Halanay, A.,Variational Problems with Delayed Argument, Delay and Functional Differential Equations, Theory and Applications, Edited by K. Schmitt, Academic Press, New York, New York, 1973.
5. Kamenskii, G. A.,Variational and Boundary-Value Problems with Deviating Argument, Differential Equations, Vol. 6, pp. 1026?1032, 1970.