@article{GDZPPN002090791, title = {Existence of Periodic Points of Maps of S1.}, journal = {Inventiones mathematicae}, volume = {20}, year = {1973}, pages = {69-74}, zbl = {0272.58005}, url = {http://dml.mathdoc.fr/item/GDZPPN002090791} }
Block, Louis; Franke, John. Existence of Periodic Points of Maps of S1.. Inventiones mathematicae, Tome 20 (1973) pp. 69-74. http://gdmltest.u-ga.fr/item/GDZPPN002090791/