@article{1250187220,
author = {Ahlbrandt, Calvin D.},
title = {Principal and antiprincipal solutions of selfadjoint differential systems and their reciprocals},
journal = {Rocky Mountain J. Math.},
volume = {2},
number = {4},
year = {1972},
pages = { 169-182},
language = {en},
url = {http://dml.mathdoc.fr/item/1250187220}
}
Ahlbrandt, Calvin D. Principal and antiprincipal solutions of selfadjoint differential systems and their reciprocals. Rocky Mountain J. Math., Tome 2 (1972) no. 4, pp. 169-182. http://gdmltest.u-ga.fr/item/1250187220/