Balibrea, Francisco, Cánovas PeñaJose S., and LópezVíctor Jiménez. “Some Invariants for σ-Permutation Maps”. Annales Mathematicae Silesianae 13 (September 30, 1999): 51-60. Accessed May 19, 2024. https://www.journals.us.edu.pl/index.php/AMSIL/article/view/14136.