@article{MZ_1974__138_172095,
     author = {J\"org Flum},
     title = {On {Horn} {Theories.}},
     journal = {Mathematische Zeitschrift},
     pages = {205--212},
     publisher = {mathdoc},
     volume = {138},
     year = {1974},
     zbl = {0275.02046},
     url = {http://geodesic.mathdoc.fr/item/MZ_1974__138_172095/}
}