@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/