The Knowledge Graph is a knowledge base used by Google and its services to enhance its search engine's results with information gathered from a variety of sources. The information is presented to users in an infobox next to the search results. Knowledge Graph infoboxes were added to Google's search engine in May 2012, starting in the United States, with international expansion by the end of the year. The information covered by the Knowledge Graph grew significantly after launch, tripling its size within seven months (covering 570 million entities and 18 billion facts) and answering "roughly one-third" of the 100 billion monthly searches Google processed in May 2016. The Knowledge Graph has been criticized for providing answers without source attribution or citation. Information from the Knowledge Graph is presented as a box, which Google has referred to as the "knowledge panel", to the right (top on mobile) of search results. According to Google, this information is retrieved from many sources, including the CIA World Factbook, Wikidata, and Wikipedia. In October 2016, Google announced that the Knowledge Graph held over 70 billion facts. There is no official documentation on the technology used for the Knowledge Graph implementation. Information from the Knowledge Graph is used to answer direct spoken questions in Google Assistant and Google Home voice queries.