A plane is a two-dimensional right vector space V over a division algebra D, which we assume in this paper has an involution; a hermitian form h : V × V −→ D is hyperbolic, if, with respect to a properly choosen basis, it is given by the matrix 0 1 1 0 ) ; the pair (V, h) is called a hyperbolic plane. If D is central simple over a number field K, a hyperbolic plane (V, h) gives rise to a reduct...
