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4. D. Bauer, E. Schmeichel, H.J. Veldman, Cycles in tough graphs — updating the last four years, in: Y. Alavi, A.J. Schwenk (Eds.), Graph Theory, Combinatorics, and Applications — Proceedings of the Seventh Quadrennial International Conference on the Theory and Applications of Graphs, Wiley, New York, 1995, pp. 19–34.
5. D. Bauer, E. Schmeichel, H.J. Veldman, Progress on tough graphs — another four years, in: Graph Theory, Combinatorics, and Applications — Proceedings of the Eighth Quadrennial International Conference on the Theory and Applications of Graphs.