@article{GDZPPN002059614,
title = {Hill Equations with Coexisting Periodic Solutions, II.},
journal = {Commentarii mathematici Helvetici},
volume = {44},
year = {1969},
pages = {381-384},
zbl = {0186.41003},
url = {http://dml.mathdoc.fr/item/GDZPPN002059614}
}
Guggenheimer, H. Hill Equations with Coexisting Periodic Solutions, II.. Commentarii mathematici Helvetici, Tome 44 (1969) pp. 381-384. http://gdmltest.u-ga.fr/item/GDZPPN002059614/