  We derive certain constraints on the reflection matrix for reflection from a
plane, nonmagnetic, optically anisotropic surface using a reciprocity theorem
stated long ago by van de Hulst in the context of scattering of polarized
light. The constraints are valid for absorbing and chiral media and can be used
as tools to check the consistency of derived expressions for such matrices in
terms of the intrinsic parameters of the reflecting medium as illustrated by
several examples.
