I attended the first ever Merlin "M" Sup course at Westland Helicopters where we were issued 4 very large books, essentially covering every topic and system. In the first book was a list of all acronyms and such like, contained within. If you went to "MCA" (minimum crutchless area) it directed you to "see thong". Sure enough there was a "thong" in the list which then referred you back to MCA.