Timeline of Google Search
21/22 Google Update". Search Engine Roundtable. Retrieved February 2, 2014. Sullivan, Danny (October 4, 2013). "Penguin 5, With The Penguin 2.1 Spam-Filtering
Timeline of Google Search
21/22 Google Update". Search Engine Roundtable. Retrieved February 2, 2014. Sullivan, Danny (October 4, 2013). "Penguin 5, With The Penguin 2.1 Spam-Filtering