@article{MM2_1977__20_154446,
     author = {Helmut Lenzing and Michael H\"oppner},
     title = {Flache und halbinjektive {Funktoren.}},
     journal = {Manuscripta mathematica},
     pages = {315--322},
     publisher = {mathdoc},
     volume = {20},
     year = {1977},
     zbl = {0354.18012},
     url = {http://geodesic.mathdoc.fr/item/MM2_1977__20_154446/}
}