Ausiello, Giorgio, Nicolas Bourgeois, Telis Giannakos, and Vangelis Th. Paschos. “Greedy Algorithms For On-Line Set-Covering”. Algorithmic Operations Research 4, no. 1 (February 3, 2009): Pages 36 - 48. Accessed October 21, 2019. https://journals.lib.unb.ca/index.php/AOR/article/view/5928.