Battelli, Flaviano, and Claudio Lazzari. 1999. “The ‘0 to ∞-Homoclinic Bifurcation’ of a Class of Discrete Two-Dimensional Maps”. Annales Mathematicae Silesianae 13 (September):73-80. https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14138.