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In order to identify research trends, Shirley Ann Williams et al, reviewed a collection of studies of the social media website Twitter, such as the 2011 paper by Celik et al, titled "Learning Semantic Relationships between Entities in Twitter." Williams's team searched for the term "Twitter" on the Scopus and Web of Science databases and found that, though most papers returned by the search did in fact focus on the social media platform, a few discussed unrelated subjects such as sounds made by tractor engines. One reasonable explanation for this result is that it occurred because____