I first was sent what seems to be a very poor reprint of the book where the binding falls off the spine, and cracked the first time I opened the book. No reference formula in the front or back cover and the paper is not your usual textbook paper with very low quality. I got sent a new copy and the difference in quality is remarkable, the new copy also contains the reference formulae in the front and back covers and has much better paper.<br><br> So just be careful! don't be afraid to return it and hopefully you won't be as unlucky as I was!