Knol is a Google project that aims to include user-written articles on a range of topics. The project was announced December 13, 2007, and was opened to the public on July 23, 2008 with a few hundred articles mostly in the health and medical field. Because there are no restrictions for sources or neutrality, knol pages are basically opinion papers of one or more authors, with many describing products for sale. Some knols are how-to articles or explain product use. Other people can post comments such as to refute opinions or reject product claims. On January 16, 2009, Google announced that Knol had grown to 100,000 articles, and users from 197 countries and territories visit Knol on an average day.
