The present perfect tense may also be used to describe research or scholarly activity that has taken
place recently
Several studies have revealed that ...
Previous studies of X have not dealt with ...
A considerable amount of literature has been published on X.
Invasive plants have been identified as major contributing factors for the decline of ....
The relationship between X and Y has been widely investigated (Smith, 1985, Jones, ...
The new material has been shown to enhance cooling properties (Smith, 1985, Jones, 1987).
There have been several investigations into the causes of illiteracy (Smith, 1985; Jones, 1987).
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