@article{MS2_1956__4_165605,
     author = {EARL A. CODDINGTON},
     title = {On maximal symmetrie ordinary differential operators},
     journal = {Mathematica Scandinavica},
     pages = {22--28},
     publisher = {mathdoc},
     volume = {4},
     year = {1956},
     zbl = {0074.06702},
     url = {http://geodesic.mathdoc.fr/item/MS2_1956__4_165605/}
}