The page contains some useful notes and presentations relating to the Measurement Equation
Here are the three original papers by Hamaker, Bregman and Sault:
HBS_one.pdf HBS_two.pdf HBS_three.pdf
The above three papers tend to use a lot of 4x4 matrices. However, after some reanalysis, Hamaker showed that one can get the same results by recasting things in terms of 2x2 matrices. This is the approach used in MeqTrees. See the paper Hamaker_four.pdf for a full discussion.
The above papers take a largely theoretical approach. A discussion which tackles a lot of practical issues relating to telescope calibration is given in JEN's famous note aips++_note185.pdf