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