The internet is like the Ouroboros, feeding on itself a constant cycle of repetition where blogs pick up information from blogs and Wikipedia passes as thorough research. Take today's cocktail for example, The Poet's Dream.
If you surf the blogosphere you'll find assertions that the Poet's Dream came from either an 30's English bar guide or the 1935 Old Waldorf Astoria Bar Book. While that's all well and good and it may have appeared in the Astoria book, but it also appeared in Jauques Straub's 1913 Straub's Manual of Mixed Drinks.
According to a 1910 issue of the Oakland Tribune Jaques Straub was a wine steward at the Blackstone Hotel in Chicago. He hailed from Switzerland and never drank, he simply knew his stuff, understood the way flavors interplay, and made the most of his skills even writing the cocktail manual Straub's Manual of Mixed Drinks. He worked at the Blackstone until prohibition did in the wine business.
Anyway, I guess the point is it's hard to know exactly where these cocktails come from. You hit on a recipe book, think you've got the source, and then a month later you find a book containing the same recipe that's a decade older. In the end, do you research, identify three agreeing sources, and you're good.