Gary L. Ebert Sebastian Egner Henk D. L. Hollmann Qing Xiang Proof of a Conjecture of De Caen and Van Dam. 201-206 2002 23 Eur. J. Comb. 2 http://dx.doi.org/10.1006/eujc.2001.0523 db/journals/ejc/ejc23.html#EbertEHX02