@article{05279365, title = {Recognizing HH-free, HHD-free, and Welsh-Powell opposition graphs.}, journal = {Discrete Mathematics and Theoretical Computer Science. DMTCS [electronic only]}, volume = {8}, year = {2006}, pages = {65-82}, zbl = {1153.05331}, language = {en}, url = {http://dml.mathdoc.fr/item/05279365} }
Nikolopoulos, Stavros D.; Palios, Leonidas. Recognizing HH-free, HHD-free, and Welsh-Powell opposition graphs.. Discrete Mathematics and Theoretical Computer Science. DMTCS [electronic only], Tome 8 (2006) pp. 65-82. http://gdmltest.u-ga.fr/item/05279365/