When the parameters are real, the hypergeometric equation defines a Schwarz triangle. We study a combinatorial-topological property of the Schwarz triangle when the three angles are not necessarily less than π.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-bc69-0-20, author = {Masaaki Yoshida}, title = {A naive-topological study of the contiguity relations for hypergeometric functions}, journal = {Banach Center Publications}, volume = {68}, year = {2005}, pages = {257-268}, zbl = {1107.33002}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-bc69-0-20} }
Masaaki Yoshida. A naive-topological study of the contiguity relations for hypergeometric functions. Banach Center Publications, Tome 68 (2005) pp. 257-268. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-bc69-0-20/