no. 3
A universal construction for projective Hjelmslev planes of level n
Compositio Mathematica, Tome 71 (1989) no. 3, pp. 285-294. 
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     author = {Hanssens, G. and Van Maldeghem, H.},
     title = {A universal construction for projective {Hjelmslev} planes of level $n$},
     journal = {Compositio Mathematica},
     pages = {285--294},
     publisher = {Kluwer Academic Publishers},
     volume = {71},
     number = {3},
     year = {1989},
     mrnumber = {1022046},
     zbl = {0709.51010},
     language = {en},
     url = {http://www.numdam.org/item/CM_1989__71_3_285_0/}
}
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Hanssens, G.; Van Maldeghem, H. A universal construction for projective Hjelmslev planes of level $n$. Compositio Mathematica, Tome 71 (1989) no. 3, pp. 285-294. http://www.numdam.org/item/CM_1989__71_3_285_0/

1 B. Artmann: Existenz und projektive Limiten von Hjelmslev-Ebenen n-ter Stufe, Atti del Convegno di Geometria Combinatoria e sue Applicazioni, Perugia (1971), 27-41. | MR | Zbl

2 D.A. Drake: Construction of Hjelmslev planes, J. Geom. 10 (1977) 179-193. | MR | Zbl

3 G. Hanssens and H. Van Maldeghem: On projective Hjelmslev planes of level n, to appear. | MR | Zbl

4 M.A. Ronan: A free construction of buildings with no rank 3 residue of spherical type, in "Buildings and the geometry of diagrams", Lect. Notes 1181, Springer-Verlag (1986) pp. 242-248. | MR | Zbl

5 H. Van Maldeghem: Non-classical triangle buildings, Geom. Ded. 24 (1987) 123-206. | MR | Zbl