@article{article091c960d,
title   = {Lines of principal curvature on canal surfaces in R³},
author = {Garcia, Ronaldo and Llibre, Jaume and Sotomayor, Jorge},
year = {2006},
doi = {10.1590/S0001-37652006000300002},
journal   = {Anais da Academia Brasileira de Ciências}
}