@article{10_5427_jsing_2020_22a,
     author = {J. C. F. Costa and L. F. Martins, and J. J. Nu\~no-Ballesteros},
     title = {On the index of principal foliations of surfaces in {R^3} with corank 1 singularities},
     journal = {Journal of Singularities},
     pages = {1--16},
     publisher = {mathdoc},
     volume = {22},
     year = {2020},
     doi = {10.5427/jsing.2020.22a},
     url = {http://geodesic.mathdoc.fr/articles/10.5427/jsing.2020.22a/}
}