75 In another major study, Zhao (1974) found that just over half of the …. In a study which set out to determine X, Smith (2012) found that …. In a randomised controlled study of X, Smith (2012) reported that …. In a large longitudinal study, Smith et al. (2012) investigated the incidence of X in Y. In one well-known recent experiment, limits on X were found to be ….. (Al-Masry, 2013) Reference to single investigations in the past: research topic as main focus To determine the effects of X, Zhao et al (2005) compared …. X was originally isolated from Y in a soil sample from …. (Wang et al., 1952). The electronic spectroscopy of X was first studied by Smith and Jones1 in 1970 X formed the central focus of a study by Smith (2002) in which the author found …. X was first demonstrated experimentally by Pavlov (Smith, 2002). In his seminal study …. Reference to what other writers do in their text: author as subject
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