@article{PIM_1991_N_S_50_64_a12,
     author = {P. G. Todorov},
     title = {A {Disproof} of a {Conjecture} of {Robertson} and {Generalizations}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {105 },
     publisher = {mathdoc},
     volume = {_N_S_50},
     number = {64},
     year = {1991},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PIM_1991_N_S_50_64_a12/}
}