1. E. Artin,Coordinates in affine geometry, Rep. Math. Coll.,2 (2) (1940), pp. 15–20.
2. E. Artin,Geometric algebra, Interscience Publishers Inc., New York (1957).
3. B. Artmann,Uniforme Hjelmslev-Ebenen und Modulare Verbände, Math. Z.,111 (1969), pp. 15–45.
4. P. Y. Bacon,Coordinatized H-planes, Ph. D. thesis, Univ. of Florida (1974).
5. V. K. Cyganova,An H-ternar of the Hjelmslev affine plane (Russian), Smolensk. Gos. Ped. Inst. Učen. Zap.,18 pp. 44–69.