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Smith (2016) states that… A number of writers have stated otherwise… As stated by Smith (2016)… On the contrary, Smith (2016) states…
…suggests that…
Barnes (2016) suggests that… Highlighting the importance of learning Barnes (2016) suggests that… A number of writers including Barnes (2016) have suggested that… This article suggests that a direction must be taken by future studies Recent evidence suggests that…
According to…
According to Davis (2016)… According to an investigation by Smith et al (2015) In addition, according to…
…defines…
The Oxford English Dictionary defines learning as… It could be defined as… Johnson defines X as follows…