@article{JRAM_1971__246_151075,
     author = {Klaus W. Roggenkamp},
     title = {Projective homomorphisms and extensions of lattices.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {41--45},
     publisher = {mathdoc},
     volume = {246},
     year = {1971},
     zbl = {0208.04204},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1971__246_151075/}
}