@article{GDZPPN002333244,
title = {An index for periodic orbits of functional differential equations.},
journal = {Mathematische Annalen},
volume = {283},
year = {1989},
pages = {381-392},
zbl = {0663.34057},
url = {http://dml.mathdoc.fr/item/GDZPPN002333244}
}
Fenske, Christian C. An index for periodic orbits of functional differential equations.. Mathematische Annalen, Tome 283 (1989) pp. 381-392. http://gdmltest.u-ga.fr/item/GDZPPN002333244/