  This paper investigates a source coding problem in which two terminals
communicating through a relay wish to estimate one another's source within some
distortion constraint. The relay has access to side information that is
correlated with the sources. Two different schemes based on the order of
communication, \emph{distributed source coding/delivery} and \emph{two cascaded
rounds}, are proposed and inner and outer bounds for the resulting
rate-distortion regions are provided. Examples are provided to show that
neither rate-distortion region includes the other one.
