Timeline of Google Search
Retrieved February 1, 2014. "Google Update Esmeralda". June 24, 2003. Retrieved February 1, 2014. "Explaining algorithm updates and data refreshes". Levy
Timeline of Google Search
Retrieved February 1, 2014. "Google Update Esmeralda". June 24, 2003. Retrieved February 1, 2014. "Explaining algorithm updates and data refreshes". Levy