English for Research: Usage, Style, and Grammar

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A.Wallwork - English for Research Usage, Style, and Grammar - 2013

8.8 present perfect vs present perfect continuous 1. If a situation has existed fora considerable number of years then the present perfect

present simple orb past simple , but to talk about what you found,
discovered, noticed etc only use the past simple .
PRESENT SIMPLE
PAST SIMPLE
1 We found that green and red produces white. This only seems to happen when the ratio of green to red is 6:1. But when the ratio is 4:1, this produces yellow. The reader may think that seems to happen and produces refer to what other people have found. We found that green and red
produced white. This only seemed to happen when the ratio of green to red was 6:1. But when the ratio
was 4:1, yellow was produced. The reader is clear that you are only talking about what you found.
2 The results are given in Table 4, which
shows that … In addition, Figure 1
highlights that X equals Y.
3 Web believeb that this means that our method outperforms all previous methods.
4 These results highlight / highlighted the importance of carrying out tests in triplicate. Web foundb that best results were achieved by carrying out tests in triplicate.

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8.8
present perfect vs present perfect continuous
1. If a situation has existed fora considerable number of years then the present perfect is preferred to present perfect continuous , if the situation is more recent then both forms can be used with the
continuous form indicating that the situation maybe temporary.
2. Do not use the present perfect continuous for completed actions or when you talk about the number of occasions that something has happened or when you specify a quantity exception years, days,
hours, minutes etc.
PRESENT PERFECT
PRESENT PERFECT CONTINUOUS
1 For thousands of years man
has tried to give a meaning to life. For several years researchers in this field

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