@article{RSMUP_1972__47__23_0,
     author = {Sachs, David},
     title = {A note on geometric mappings},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {23--28},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {47},
     year = {1972},
     mrnumber = {319793},
     zbl = {0266.06006},
     language = {en},
     url = {http://archive.numdam.org/item/RSMUP_1972__47__23_0/}
}