You must, yes must, use the new 2017 4th Edition of the Encyclopedia of Counseling, The Authentic Purple Book. No exceptions!!! Yes, a lot of the material is the same as the previous edition, but a ton of new information has been added. The new book is nearly 100 pages longer and contains numerous topics that didn't even exist when the Special 25th Anniversary Edition of the Encyclopedia of Counseling was released. Every section of the new edition contains new information, updates, and deletions. Okay, so just to be certain that you are 100% clear, it doesn't make any difference what other materials you are using, you must use the new version of the Encyclopedia.