I just ordered 'Beyond the Zone System' by Phil Davis, but it would seem that I ordered the 1981 edition by mistake. I know the book is at its 4th addition now, and so I was wondering if there have been a lot of significant changes from the 1st to 4th edition. I mainly want to learn about this system to gain better control of my materials. Do I really need the lastest edition, or will this one suffice? Thanks for any help!