Check out this great article on Hanna Barbera from the September 1960 issue from Popular Mechanics (that’s Carlo Vinci above shown animating Fred Flintstone). I found it using the new feature on Google’s Book Search which now includes magazines. It’s unclear how many magazines are currently in their system, but at launch it seems to include New York magazine, Popular Mechanics, Popular Science, Ebony, Jet, Vegetarian Times, and Baseball Digest.
For example, a quick search for Disney or Animation brings up articles like this 1945 classic from Popular Science about how Disney combines live action and animation. This looks to be a great resource for us as they add more periodicals.