@article{10_4153_CJM_1984_029_4,
     author = {Kn\"uppel, Frieder},
     title = {A {Class} of {Homomorphisms} of {Pre-Hjelmslev} {Groups}},
     journal = {Canadian journal of mathematics},
     pages = {470--494},
     year = {1984},
     volume = {36},
     number = {3},
     doi = {10.4153/CJM-1984-029-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1984-029-4/}
}