1. C. Berge, Graphes et Hvpergraphes. Dunod Editeur, Paris 1970.
2. D. Gale, Optimal assignments in an ordered set: an application of matroid theory, J. Comb. Theory 4 (1968), 176–180.
3. R. Halin, Graphentheorie I. II. Wissenschaftliche Buchgesellschaft Darmstadt, Darmstadt, FRG, 1980, 1981.
4. E. Horovitz, S. Sahni. Fundamentals of Computer Algorithms. Computer Science Press Inc., Potomac Maryland 1978.
5. V. Klee, The greedy algorithm for finitary and cofinitary matroids, Combinatorics (T.S. Motzkin. ed.). Proc. Symposium in Pure Math., vol. XIX, Amer. Math. Soc. 1971.