1. L. Armijo, “Minimization of functionals having Lipschitz continuous first partial derivatives”,Pacific Journal of Mathematics 16 (1966) 1–3.
2. R.P. Brent,Algorithms for minimization without derivatives (Prentice-Hall, Englewood Cliffs, N.J., 1972).
3. F.L. Chernous'ko, “A local variation method for the numerical solution of variational problems”,Žurnal Vyčslitel'noį Matematiki i Matematičeskoį Fiziki 5 (1965) 749–754 [in Russian; English transl.:U.S.S.R. Computational Mathematics and Mathematical Physics 5 (1965) 234–2421.
4. J. Cullum, “Unconstrained minimization of functions without explicit use of their derivatives”, IBM Watson Research Center, Yorktown Heights, N.Y. (1971).
5. J.W. Daniel,The approximate minimization of functionals (Prentice-Hall, Englewood Cliffs, N.J., 1971).