Fixed points, periodic points, and coin-tossing sequences for mappings defined on two-dimensional cells. Papini, Duccio; Zanolin, Fabio — 2004 Fixed Point Theory and Applications [electronic only]
Periodic points and chaotic-like dynamics of planar maps associated to nonlinear Hill's equations with indefinite weight. Papini, Duccio; Zanolin, Fabio — 2002 Georgian Mathematical Journal