@article{GDZPPN002473909,
title = {Some Properties of Solutions of u'' + a(t) f(u) = 0.},
journal = {Monatshefte f\"ur Mathematik},
volume = {67},
year = {1963},
pages = {50-54},
zbl = {0116.29401},
url = {http://dml.mathdoc.fr/item/GDZPPN002473909}
}
Waltman, P. Some Properties of Solutions of u'' + a(t) f(u) = 0.. Monatshefte für Mathematik, Tome 67 (1963) pp. 50-54. http://gdmltest.u-ga.fr/item/GDZPPN002473909/