@article{AM2_1987__33_137208,
     author = {C. Alsina and A. Sklar},
     title = {A characterization of continuous associative operations whose graphs are ruled surfaces.},
     journal = {Aequationes mathematicae},
     pages = {114--119},
     publisher = {mathdoc},
     volume = {33},
     year = {1987},
     zbl = {0625.39008},
     url = {http://geodesic.mathdoc.fr/item/AM2_1987__33_137208/}
}