@article{1255380829, author = {Feller, William}, title = {On the intrinsic form for second order differential operators}, journal = {Illinois J. Math.}, volume = {2}, number = {1}, year = {1958}, pages = { 1-18}, language = {en}, url = {http://dml.mathdoc.fr/item/1255380829} }
Feller, William. On the intrinsic form for second order differential operators. Illinois J. Math., Tome 2 (1958) no. 1, pp. 1-18. http://gdmltest.u-ga.fr/item/1255380829/