@article{NUMA_1965__7_131638,
     author = {J.S. MAYBEE},
     title = {Some {Structural} {Theorems} for {Partial} {Difference} {Operators.}},
     journal = {Numerische Mathematik},
     pages = {66--72},
     year = {1965},
     volume = {7},
     zbl = {0141.28502},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1965__7_131638/}
}