In article , "Jonathan
Thornburg [remove -animal to reply]"
writes:

Can someone point me to a good explanation of this method ? I.e. by
analysing lensing effects in a galaxy cluster, it is possible to map
the distribution of DM within the cluster, and presumably also to
estimate the amount of DM present in the cluster.

A nice black-marks-on-dead-trees review is

Peter Schneider, Christopher S. Kochanek, and Joachim Wambsganss,
"Gravitational Lensing: Strong, Weak and Micro"
(Saas-Fee Advanced Course 33)
Springer-Verlag, 2006, ISBN 978-3-540-30309-1

This covers essentially all of gravitational lensing, though, not just
what the OP was looking for. Still, no reason not to read it.