71 Several attempts have been made to …. (Smith, 1996; Jones 1999; ….). Several studies thus far have linked X with Y (Smith, 2002; Jones 2004; ….). Several studies have revealed that it is not just X that acts on ….. (Smith, 1996; Jones …. Several biographies of Brown have been published. Smith (2013) presents ….. The geology of X has been addressed in several smallscale investigations and …. Data from several sources have identified the increased X and Y associated with obesity. Previous studies have reported …. (Smith, 1985; Jones, 1987; Johnson, 1992). Previous research has indicated that various X indicators have a positive impact on …. Previous research findings into X have been inconsistent and contradictory (Smith, 1996; ….) Numerous studies have attempted to explain …. (for example, Smith , 1996; Kelly, 1998; ….) A number of authors have reported analyses of trends in X that demonstrated …. A number of studies have found that …. (Smith , 2003; Jones, 2004).
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