@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/