Completing a Tetrahedron to a Parallelepiped
This Demonstration shows a completion of a tetrahedron to a parallelepiped . The four vertices of are vertices of , and the edges of become four diagonals on the faces of .
The construction is described in [1, pp. 106–107].
 V. V. Prasolov and I. F. Sharygin, Problems in Stereometry (in Russian), Moscow: Nauka, 1989.