  In gravitational lens systems with 3 or more resolved images of a quasar, the
intrinsic variability may be unambiguously separated from the microlensing
variability through parallax measurements from 3 observers when there is no
relative motion of the lens masses (Refsdal 1993). In systems with fewer than 3
resolved images, however, this separation is not straightforward. A general
approach that may be used for this purpose is presented. For simplicity, only
the one-dimensional case is considered in detail: Given a well-sampled time
series of the observed flux at two points in space with a known separation,
choosing a velocity $v_{\perp}$ of the observers perpendicular to the line of
sight determines the microlensing magnification history, and thereby also the
intrinsic variability. The velocity is chosen by minimizing some measure
($\chi^2$) of the residual intrinsic variability. In many cases this gives a
close approximation to the true magnification. In cases where the relative
motion of the lensing point masses is important, only a partial separation will
be possible.
