@article{CMUC_1967_8_2_a0,
     author = {Cenkl, Bohumil},
     title = {The elliptic differential operators},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {175--197},
     year = {1967},
     volume = {8},
     number = {2},
     mrnumber = {0232409},
     zbl = {0157.18302},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1967_8_2_a0/}
}