@article{10_21136_CMJ_1980_101659,
     author = {Etgen, Garret J. and Lewis, Roger T.},
     title = {A {Hille-Wintner} comparison theorem for second order differential systems},
     journal = {Czechoslovak Mathematical Journal},
     pages = {98--107},
     publisher = {mathdoc},
     volume = {30},
     number = {1},
     year = {1980},
     doi = {10.21136/CMJ.1980.101659},
     mrnumber = {565912},
     zbl = {0429.34033},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1980.101659/}
}