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[2] F. Harary: Graph Theory. Addison-Wesley, Reading, Mass. 1969. MR 0256911 | Zbl 0196.27202

[3] F. Harary R. M. Karp, W. T. Tutte: A Criterion for Planarity of the Square of a Graph. J. Combinatorial Theory 2 (1967), 395-405. DOI 10.1016/S0021-9800(67)80050-4 | MR 0216976