@article{ELMA_1988__43_3_141419,
     author = {G.L. Cohen and G.H. Smith},
     title = {A proof of {Ilieff's} conjecture for polynomials with four zeros.},
     journal = {Elemente der Mathematik},
     pages = {18--21},
     publisher = {mathdoc},
     volume = {43},
     number = {3},
     year = {1988},
     zbl = {0699.30006},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1988__43_3_141419/}
}