Scot A. Reader's Inside T206 is a great primer and useful roadmap for understanding these iconic cards. The book(let)/paper (I'm not sure how it is classified) can be downloaded as a .pdf file through the T206 Museum.com.
I finished reading it on Friday. He mentions these ads in the Sporting Life, but doesn't include any images in his paper. A quick websearch (and a bit of a decent memory) pointed me to la84foundation.org.
I do wish that Mr. Reader would have included a few images (of these ads, but mostly of the backs of the cards which I find almost as intriguing as the fronts. A few photos of the fronts of the cards wouldn't hurt, either.)
I'm not being critical in the catty sort of way, just my thoughts. And I wanted to let both my readers know that I don't come up with this stuff on my own.