@article{GDZPPN002479516, title = {On the Solutions of (ry')' + qy = f.}, journal = {Monatshefte f\"ur Mathematik}, volume = {79}, year = {1975}, pages = {115-118}, zbl = {0323.34029}, url = {http://dml.mathdoc.fr/item/GDZPPN002479516} }
Krall, Allan M. On the Solutions of (ry')' + qy = f.. Monatshefte für Mathematik, Tome 79 (1975) pp. 115-118. http://gdmltest.u-ga.fr/item/GDZPPN002479516/