1. D.P. Bertsekas and S.K. Mitter, “Steepest descent for optimization problems with nondifferentiable cost functions,” Proceedings of the 5th Annual Princeton Conference on Information Sciences and Systems, 1971.
2. Jane Cullum and W.E. Donath, “A block generalization of the symmetric s-step Lanczos algorithm”, IBM RC 4845 (May 1974).
3. Jane Cullum, W.E. Donath and P. Wolf, “An algorithm for minimizing certain non-differentiable convex functions”, IBM RC 4611 (November 1973).
4. Haskell B. Curry, “The method of steepest descent for nonlinear minimization problems,” Quarterly of Applied Mathematics 2, 258–261.
5. John Danskin, The theory of max-min (Springer, Berlin, 1964).