@article{MZ_1991__208_3_174342,
     author = {F. Mil\'an and A. Mart{\'\i}nez},
     title = {On affine-maximal ruled surfaces.},
     journal = {Mathematische Zeitschrift},
     pages = {635--644},
     publisher = {mathdoc},
     volume = {208},
     number = {3},
     year = {1991},
     zbl = {0754.53016},
     url = {http://geodesic.mathdoc.fr/item/MZ_1991__208_3_174342/}
}