  We show that the Einstein ring radius and transverse speed of a lens
projected on the source plane, $\hat{r}_{\rm e}$ and $\hat{v}$, can be
determined from the light curve of a binary-source event, followed by the
spectroscopic determination of the orbital elements of the source stars. The
determination makes use of the same principle that allows one to measure the
Einstein ring radii from finite-source effects. For the case when the orbital
period of the source stars is much longer than the Einstein time scale, $P\gg
t_{\rm e}$, there exists a single two-fold degeneracy in determining
$\hat{r}_{\rm e}$. However, when $P \lesssim t_{\rm e}$ the degeneracy can
often be broken by making use of the binary-source system's orbital motion.
%Once $\hat{r}_{\rm e}$, and thus $\hat{v}$ are determined, one can
%distinguish self-lensing events in the Large Magellanic Cloud %from Galactic
halo events. For an identifiable 8\% of all lensing events seen toward the
Large Magellanic Cloud (LMC), one can unambiguously determine whether the
lenses are Galactic, or whether they lie in the LMC itself. The required
observations can be made after the event is over and could be carried out for
the $\sim 8$ events seen by Alcock et al.\ and Aubourg et al.. In addition, we
propose to include eclipsing binaries as sources for gravitational lensing
experiments.
