@article{1250130565,
author = {Zettl, A.},
title = {Formally self-adjoint quasi-differential operators},
journal = {Rocky Mountain J. Math.},
volume = {5},
number = {4},
year = {1975},
pages = { 453-474},
language = {en},
url = {http://dml.mathdoc.fr/item/1250130565}
}
Zettl, A. Formally self-adjoint quasi-differential operators. Rocky Mountain J. Math., Tome 5 (1975) no. 4, pp. 453-474. http://gdmltest.u-ga.fr/item/1250130565/