@article{10_1017_S0017089500007837,
     author = {Hanssens, G. and Maldeghem, H. van},
     title = {On projective {Hjelmslev} planes of level n},
     journal = {Glasgow mathematical journal},
     pages = {257--261},
     year = {1989},
     volume = {31},
     number = {3},
     doi = {10.1017/S0017089500007837},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500007837/}
}