Voir la notice de l'article provenant de la source Czech Digital Mathematics Library
@article{MASLO_1980__30_3_a12, author = {Gera, Milan}, title = {\"Uber die {Untermengen} der {L\"osungen} der {Gleichung} $x'''+a(t)x"+b(t)x'+c(t)x= 0 c(t)\geq 0$}, journal = {Mathematica slovaca}, pages = {313--326}, publisher = {mathdoc}, volume = {30}, number = {3}, year = {1980}, mrnumber = {587259}, zbl = {0443.34034}, language = {ge}, url = {http://geodesic.mathdoc.fr/item/MASLO_1980__30_3_a12/} }
Gera, Milan. Über die Untermengen der Lösungen der Gleichung $x'''+a(t)x"+b(t)x'+c(t)x= 0 c(t)\geq 0$. Mathematica slovaca, Tome 30 (1980) no. 3, pp. 313-326. http://geodesic.mathdoc.fr/item/MASLO_1980__30_3_a12/