1. Hildebrand, F.B. (1956), Introduction to numerical analysis, McGraw-Hill (New York).
2. Kruskal, J.B. (1964), “Nonmetric multidimensional scaling: a numerical method”, Psychometrika, Vol. 29, pp. 115–129.
3. Powell, M.J.D. (1981), Approximation theory and methods, Cambridge University Press (Cambridge).
4. Ubhaya, V.A. (1977), “An O(n) algorithm for discrete n-point convex approximation with applications to continuous case”, Technical Memorandum No. 434 (Operations Research Dept., Case Western Reserve University).