Comment by davidsong

Well, it is every version of RAR. Documenting the quirks of rar 1.4, 1.5, 2.0, 2.9, 3.0, 4.0, 5.0 and 7.0, multiple compression strategies, PPMd, RARVM, compression levels, encryption, multi volume support, a huge test corpus, round trips for compatibility... The spec docs are linked.