This preprint of Jürgen Abel gives a short introduction into the BWCA field and proposes several improvements for the WFC stage and the IF stage.
It further introduces a new RLE scheme for bypassing the run length
information around the WFC stage. The paper is the basis of the
BWCA program ABC and the revealed approach achieves a
compression rate of 2.238 bps, which is the best result for a pure
BWCA without any preprocessing before the BWT to date (March 2003).

http://www.data-compression.info/JuergenAbel/Preprints/Preprint_After_BWT_Stages.pdf