Translation:They wrote that article in their PhD.
And by the way, what is the meaning of "in their Ph.D."? If it is for a doctoral thesis, the sentence should be, "for their PhD", even if it refers to only a part of it. If you have another explanation, I'm all eyes and ears.
Grammarly keeps bugging me to make the designation of "doctor of philosophy" Ph.D. So, please make it acceptable here as well.
Thank you for your patience.
Yes, there's a difference, but "this" should be correct here. This article = המאמר הזה That article = המאמר ההוא . This sentence is weird in any case. One can't write anything in one's PhD. You either write the paper during your doctoral STUDIES, or you write it as part of your PhD DISSERTATION.