  It is shown that the expressions for the tangential pressure, the anisotropy
factor and the radial pressure in the Einstein - Maxwell equations may serve as
generating functions for charged stellar models. The latter can incorporate an
equation of state when the expression for the energy density is also used.
Other generating functions are based on the condition for the existence of
conformal motion (conformal flatness in particular) and the Karmarkar condition
for embedding class one metrics, which do not depend on charge. In all these
cases the equations are linear first order differential equations for one of
the metric components and Riccati equations for the other. The latter may be
always transformed into second order homogenous linear differential equations.
These conclusions are illustrated by numerous particular examples from the
study of charged stellar models.
