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Graphs and Digraphs. Prindle, Weber and Schmidt, Boston 1979.
MR 0525578
[2] CHARTRAND G., GOULD R. J., KAPOOR S. F.: Bigraphical sequences. submitted for publication.
[3] ERDOS P., KELLY P.:
The minimal regular graph containing a given graph. A Seminar on Graph Theory (F. Harary Ed.) Holt, Rinehart and Winston, New York 1967, 65-69.
MR 0223264