@article{02247402,
title = {Invariant transformations for the Sturm--Liouville operator.},
journal = {Zapiski Nauchnykh Seminarov POMI},
volume = {321},
year = {2005},
pages = {25-54},
zbl = {1136.34066},
language = {en},
url = {http://dml.mathdoc.fr/item/02247402}
}
Vagharshakyan, A. Invariant transformations for the Sturm--Liouville operator.. Zapiski Nauchnykh Seminarov POMI, Tome 321 (2005) pp. 25-54. http://gdmltest.u-ga.fr/item/02247402/