PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY, vol. 134, no. 9, page. 2711 - 2718, 2006-01
ARS COMBINATORIA, vol. 77, page. 233 - 244, 2005-10
JOURNAL OF COMBINATORIAL THEORY SERIES A, vol. 98, no. 1, page. 60 - 73, 2002-04