I am going to be taking the April 2019 HVAC/Refrigeration exam and have been reviewing this forums recommendations for study material. I have an older copy of MERM (11th edition I believe), and access to a full set of ASHRAE handbooks...but the ASHRAE handbooks are 1998-2001. Can anyone advise if it's necessary to shell out for the newest versions of the books, or if these may be sufficient? I may be able to print a chapter here and there from digital copies of the newer books, but I'd want to keep that at a minimum.