KOLYADA, Sergiy - SNOHA, Ľubomír - TROFIMCHUK, Sergei. Noninvertible minimal maps. In Fundamenta Mathematicae. - Warsaw : Polish Acad Sciences Inst Mathematics, 2001, 2001, vol. 168, issue 2, p. 141-163. Available on: https://doi.org/10.4064/fm168-2-5.