Competition Graphs of Hamiltonian Digraphs
David R. Guichard · SIAM Journal on Discrete Mathematics · 1998
K. F. Fraughnaugh et al. proved that a graph G is the competition graph of a hamiltonian digraph possibly having loops if and only if G has an edge clique cover ${\cal C}=\{C_1,\ldots,C_n\}$ that has a system of distinct representatives. [SIAM J. Discrete Math., 8 (1995), pp. 179--185]. We settle a question left open by their work, by showing that the words "possibly having loops" may be removed.