Thakare, N. K., S. Maeda, and B. N. Waphare. “Modular Pairs, Covering Property and Related Results in Posets”. The Journal of the Indian Mathematical Society 70, no. 1-4 (December 1, 2003): 229–253. Accessed May 3, 2024. https://www.informaticsjournals.com/index.php/jims/article/view/21984.