A partial solution for lossless source coding with coded side information

This paper considers the problem, first introduced by Ahlswede and Korner in 1975, of lossless source coding with Coded side information. Specifically, let X and Y be two random variables such that X is desired losslessly at the decoder while Y serves as side information. The random variables are encoded independently, and both descriptions are used by the decoder to reconstruct X. AhIswede and Korner describe the achievable rate region in terms of an auxiliary random variable. This paper gives a partial solution for the optimal auxiliary random variable, thereby describing part of the rate region explicitly in terms of the distribution of X and Y.