@article{article95e9b64e,
title   = {Polar multiplicities and Euler obstruction for ruled surfaces},
author = {Grulha Júnior, Nivaldo de Góes and Hernandes, Marcelo E and Martins, Rodrigo},
year = {2012},
doi = {10.1007/s00574-012-0021-3},
journal   = {Bulletin of the Brazilian Mathematical Society}
}