@article{10_4153_CJM_1979_068_5,
     author = {Kn\"uppel, Frieder and Kunze, Michael},
     title = {Neighbor {Relation} and {Neighbor} {Homomorphism} of {Hjelmslev} {Groups}},
     journal = {Canadian journal of mathematics},
     pages = {680--699},
     year = {1979},
     volume = {31},
     number = {4},
     doi = {10.4153/CJM-1979-068-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1979-068-5/}
}