1. Wallis, W. D.: The smallest regular graphs without one-factors. Ars Combin., 11, 295–300 (1981)
2. Zhao, C.: The disjoint 1-factors of (d, d + 1)-graphs. J. Combin. Math. Combin. Comput., 9, 195–198 (1991)
3. Tutte, W. T.: The factorizations of linear graphs. J. London Math. Soc., 22, 459–474 (1947)
4. Volkmann, L., Zingsem, A.: On the order of almost regular bipartite graphs without perfect matchings. Australas. J. Combin., 42, 165–170 (2008)
5. Caccetta, L., Mardiyono, S.: On the existence of almost-regular-graphs without one-factors. Australas. J. Combin., 9, 243–260 (1994)