Encoding of Functions of Correlated Sources
  This submission is being withdrawn due to serious errors in the achievability proofs. The reviewers of the journal I had submitted to had found errors back in 2006. I had forgotten about this paper until I saw the CFP for a JSAC issue on in-network computation. http://www.jsac.ucsd.edu/Calls/in-networkcomputationcfp.pdf. 
Saravanan Vijayakumaran