@article{1102710094,
author = {Butler, G. J. and Erbe, L. H.},
title = {Comparison theorems for second-order operator-valued linear differential equations.},
journal = {Pacific J. Math.},
volume = {115},
number = {2},
year = {1984},
pages = { 21-34},
language = {en},
url = {http://dml.mathdoc.fr/item/1102710094}
}
Butler, G. J.; Erbe, L. H. Comparison theorems for second-order operator-valued linear differential equations.. Pacific J. Math., Tome 115 (1984) no. 2, pp. 21-34. http://gdmltest.u-ga.fr/item/1102710094/