Robles, Gemma, and José M. Méndez. “A Class of Simpler Logical Matrices for the Variable-Sharing Property”. Logic and Logical Philosophy 20, no. 3 (November 30, 2011): 241–249. Accessed January 25, 2022. https://apcz.umk.pl/LLP/article/view/LLP.2011.014.