1
Schaefer M. The Graph Crossing Number and its Variants: A Survey[J]. Electronic Journal of Combinatorics, 2013, 1000(0).
2
Kreuzer A. A system of axioms for projective Hjelmslev spaces[J]. Journal of Geometry, 1991: 125-147.
3
Pollard S. Fundamental Questions of Geometry[C]., 2010: 45-49.
4
Dirk Keppens. Laguerre and Minkowski planes with neighbor relation. 1987.
5
Hall J L. Mutually unbiased bases and related structures[C]., 2011.
6
Werner Seier. Über Hjelmslev-Strukturen II. 1974.
7
Werner Seier. Über Hjelmslev-Strukturen I. 1974.
8
Emanuel Kolb. Hjelmslev planes over nearrings. 1996.
9
Konrad Lang. Spiegelungen in Hjelmslev'schen Kreisgeometrien. 1986.
10
Combinatorics. Laguerre and Minkowski planes with neighbor relation. 1987.