@article{article35bef6a7,
title   = {Three theorems on gradient fields potentially useful in homing pigeon navigation},
author = {Garcia, Manuel Valentim de Pera and Possani, Claudio and Ranvaud, Ronald and Tal, Fábio Armando},
year = {2005},
doi = {10.1007/s00285-005-0340-8},
journal   = {Journal of Mathematical Biology}
}