An interesting trick to locate PDF files on google about gambling lies in adding "filetype: pdf" to the search term.
You can find a little bit of everything: essays from universities, crass advertisements and even commercial systems at no cost.
roulette system filetype:pdf
https://www.google.co.ve/search?q=roulette+system+filetype:pdf
baccarat system filetype:pdf
https://www.google.co.ve/search?q=baccarat+system+filetype:pdf
gambling system filetype:pdf
https://www.google.co.ve/search?q=gambling+system+filetype:pdf
Another interesting site to find files: Bookzz.org
gambling
http://bookzz.org/s/?q=gambling&t=0
Thanks WW!
Now just to find time for reading...
when you have some time to burn off:
https://archive.org/search.php?query=roulette
https://archive.org/search.php?query=gambling
More here: http://avaxhm.com/ebooks/gambling