You might be safe with reading expired patents, but don't take my word for it. I do sometimes and get a kick out of it. Where would we be without a patent for a

You might be safe with reading expired patents, but don't take my word for it. I do sometimes and get a kick out of it. Where would we be without a patent for a "Baseball cap for pigtail hairstyles"? http://www.latepatents.net/5799334.htm http://www.latepatents.net/5799334.htm (Their site seems to be dead in places, but you can still browse through a few of them with google https://www.google.com/search?q=site:latepatents.net https://www.google.com/search?q=site:latepatents.net ) Academic papers at Arxiv and elsewhere are far more useful.