@article{MZ_1956__64_169561,
     author = {C.R. Putnam},
     title = {A {Note} on {Inverses} of {Differential} {Operators.}},
     journal = {Mathematische Zeitschrift},
     pages = {149--150},
     publisher = {mathdoc},
     volume = {64},
     year = {1956},
     zbl = {0070.12104},
     url = {http://geodesic.mathdoc.fr/item/MZ_1956__64_169561/}
}