@article{10_4153_CMB_1991_038_3,
     author = {Lanteri, Antonio},
     title = {Vertically of {(-1)-Lines} in {Scrolls} {Over} {Smooth} {Surfaces}},
     journal = {Canadian mathematical bulletin},
     pages = {236--239},
     year = {1991},
     volume = {34},
     number = {2},
     doi = {10.4153/CMB-1991-038-3},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1991-038-3/}
}