1. 1. Bellman R. (1959) Functional equations in the theory of dynamic programming, XI-Limit theorems, Rand. Circolo Math. Palermo 8(3):343–345
2. 2. Bellman R., Kalaba R. (1965) Dynamic programming and modern control theory. Academic Press, New York and London
3. 3. Christofides N., Graph Theory: An Algorithmic Approach, Academic Press, New York, London, San Francisco (1975).
4. 4. Karp R. (1978) A characterization of the minimum cycle mean in a digraph. Discrete Mathematics 23(3):309–311
5. Lawler E., Optimal cycles in doubly weighted directed linear graphs. Int. Symp. on Theory of Graphs, Dunod, Paris, p. 209, (1996).