C chemistry123 New Member 7+ Year Member Joined Jul 10, 2015 Messages 9 Reaction score 0 Jul 11, 2015 #1 Members don't see this ad. How much does Dr. Collins materials change year by year? Thanks!
Jasontx New Member 7+ Year Member Joined Jul 10, 2015 Messages 5 Reaction score 0 Jul 11, 2015 #2 Same question, I have dr. Collins update 2014 and wonder if I should buy the 2015? Upvote 0 Downvote
