@article{NUMA_1984__43_132892,
     author = {Marino Zennaro},
     title = {Maximum {Principles} for {Linear} {Difference-Differential} {Opeartors} in {Periodic} {Function} {Spaces.}},
     journal = {Numerische Mathematik},
     pages = {121--140},
     publisher = {mathdoc},
     volume = {43},
     year = {1984},
     zbl = {0509.34070},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1984__43_132892/}
}