@article{2265,
author = {Barrett, John H.},
title = {Matrix systems of second order differential equations},
journal = {Portugaliae mathematica},
volume = {14},
year = {1955},
pages = {79-89},
zbl = {0066.33703},
mrnumber = {0080219},
language = {en},
url = {http://dml.mathdoc.fr/item/2265}
}
Barrett, John H. Matrix systems of second order differential equations. Portugaliae mathematica, Tome 14 (1955) pp. 79-89. http://gdmltest.u-ga.fr/item/2265/