Q: Should I use 'was' or 'is' in the following sentence?
How should I write about the previous study in a review article? Say I have to write: 'AZ et al. in their 2010 study found that drug B --- more helpful than drug A.' Should I write 'was' or 'is'? Which is correct? I have read many review articles in which the author uses them alternatively.
Yes, you are right. The use of tense varies in academic writing and is quite keenly debated. Anyway, as you are writing a review article, you may refer to this resource/query as a guide: What tense should I use when writing a literature review? On going through it, you will find that, in this case, as your focus is more on the study and the researchers (rather than your views on it), it would be better to go with 'was.'