There are plenty of sources and the original papers are easily found, but there isn't a proper bibliography with links which I agree is frustrating. For example the first one says the last name of the author and the year: Andreasson and 1987. So I googled "Andreasson 1987 cannabis" and found the article:

http://www.thelancet.com/journals/lancet/article/PIIS0140-67...

Hope this helps.