I found his (Yann's) blog posts the most helpful for getting a basic idea of what was going on with FSE: https://fastcompression.blogspot.com/2013/12/finite-sta

I found his (Yann's) blog posts the most helpful for getting a basic idea of what was going on with FSE: https://fastcompression.blogspot.com/2013/12/finite-state-entropy-new-breed-of.html https://fastcompression.blogspot.com/2013/12/finite-state-en... and the followup https://fastcompression.blogspot.fr/2014/01/fse-decoding-how-it-works.html https://fastcompression.blogspot.fr/2014/01/fse-decoding-how...