Hyperbolic projective-metric planes, first axiomatized by R. Lingenberg [7], are shown to be axiomatizable in terms of lines and orthogonality.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-ba52-3-9, author = {Victor Pambuccian}, title = {An Axiomatics for Hyperbolic Projective-Metric Planes in Terms of Lines and Orthogonality}, journal = {Bulletin of the Polish Academy of Sciences. Mathematics}, volume = {52}, year = {2004}, pages = {297-302}, zbl = {1101.51007}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ba52-3-9} }
Victor Pambuccian. An Axiomatics for Hyperbolic Projective-Metric Planes in Terms of Lines and Orthogonality. Bulletin of the Polish Academy of Sciences. Mathematics, Tome 52 (2004) pp. 297-302. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ba52-3-9/