That's a good one. A lot of FREE info can be found on NOFMA's website. Go here:
http://www.nofma.org/
Now click on the tab that says publications. It's on the left. You'll come to a search page. Click on the drop down menu called "All Publications" and you'll see 4 catagories. All are good but the general section doesn't have much real info. Click on any of the other three catagories and hit search. It'll bring you to a menu of various articles and publications. Click on the pdf logo to dowload the publication for FREE. Excellent stuff there.