The Wayback Machine - https://web.archive.org/web/20200203072736/https://news.ycombinator.com/submitlink?u=http%3A%2F%2Fwww.ebookreaderguide.com%2F2011%2F03%2F13%2Fkindle-nookcolor-ipad2-sony-overdrive-which-ebookstore-has-most-ebook-titles%2F&t=Survey%20of%20Kindle%2C%20Nook%2C%20iPad%2C%20Sony%20and%20OverDrive%20eBook%20Store%20Collection%20Size