  Cappellari (2008) presented a flexible and efficient method to model the
stellar kinematics of anisotropic axisymmetric and spherical stellar systems.
The spherical formalism could be used to model the line-of-sight velocity
second moments allowing for essentially arbitrary radial variation in the
anisotropy and general luminous and total density profiles. Here we generalize
the spherical formalism by providing the expressions for all three components
of the projected second moments, including the two proper motion components. A
reference implementation is now included in the public JAM package available at
http://purl.org/cappellari/software
