@article{GDZPPN002081857, title = {A proof of Ilieff's conjecture for polynomials with four zeros.}, journal = {Elemente der Mathematik}, volume = {43}, year = {1988}, pages = {18-21}, zbl = {0699.30006}, url = {http://dml.mathdoc.fr/item/GDZPPN002081857} }
Cohen, G.L.; Smith, G.H. A proof of Ilieff's conjecture for polynomials with four zeros.. Elemente der Mathematik, Tome 43 (1988) pp. 18-21. http://gdmltest.u-ga.fr/item/GDZPPN002081857/