ORDER-A JOURNAL ON THE THEORY OF ORDERED SETS AND ITS APPLICATIONS, vol. 22, no. 1, page. 63 - 72, 2005-02
KUWAIT JOURNAL OF SCIENCE & ENGINEERING, vol. 33, no. 2, page. 19 - 32, 2006-12
DISCRETE MATHEMATICS, vol. 148, no. 1-3, page. 85 - 105, 1996-01-15