@article{GDZPPN002344327, title = {On maximal symmetrie ordinary differential operators}, journal = {Mathematica Scandinavica}, volume = {4}, year = {1956}, pages = {22-28}, zbl = {0074.06702}, url = {http://dml.mathdoc.fr/item/GDZPPN002344327} }
CODDINGTON, EARL A. On maximal symmetrie ordinary differential operators. Mathematica Scandinavica, Tome 4 (1956) pp. 22-28. http://gdmltest.u-ga.fr/item/GDZPPN002344327/