Any complete plane quadrilateral can serve as the parallel projection of a tetrahedron similar to a given one.
The theorem was first stated in a different form by K. Pohlke (1853), and was generalized by H.A. Schwarz (1864).
|||P.S. Alexandroff [P.S. Aleksandrov] (ed.) et al. (ed.) , Enzyklopaedie der Elementarmathematik , 4. Geometrie , Deutsch. Verlag Wissenschaft. (1967) (Translated from Russian)|
Pohlke-Schwarz theorem. Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Pohlke-Schwarz_theorem&oldid=22909