View source for Parallelism axiom

The axiom defining the relationship of parallelism in various geometries. See [[Parallel straight lines|Parallel straight lines]]; [[Fifth postulate|Fifth postulate]].

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<table><TR><TD valign="top">[a1]</TD> <TD valign="top">  D. Hilbert,   "Grundlagen der Geometrie" , Teubner, reprint  (1968)</TD></TR><TR><TD valign="top">[a2]</TD> <TD valign="top">  H.S.M. Coxeter,   "Introduction to geometry" , Wiley  (1969)  pp. 185–186; 396–404</TD></TR></table>