Is it advisable to cite papers in PhD Statement of Purpose? I found out some similar questions, such as https://www.quora.com/Should-I-cite-papers-in-my-Statement-of-Purpose, Is it advisable to use formal citations in a statement of purpose?. However, I think my question is more specific.

I am preparing statement of purpose for PhD in Material Science (in US). I have some professors in mind to work with. To demonstrate on what problems I would to work, should I formally cite the professor's paper in Statement of Purpose? The idea is not to write a technical paper but to illustrate on what problems I would like to work.

If someone does not write citations, how would you convey what problems you would like to work on? I think that it would be too generic just to describe research interests. I see some pros in citations:


Being specific in what you want to do 
Indicating you studied professor's work and showing interest in the professor's research.


Is citing papers statement of purpose a normal practice?
For the specific question of "should I cite a paper by one of my people of interest whom I want to read this application", I don't see a reason why you couldn't. I think there is no way in which your question, at the high level, is any different from the others you referenced. 

However, there is more subtext to your decision to cite this professor. "I know your work", you want to say: "I'm ahead on my literature. I stay up to date." Well, you need to be careful making that statement because you could totally be wrong and not know better. If you say you want to work on exciting new problems and pick a 2012 paper (it's the latest on his CV!) where the conclusion is "this field is tapped out", the professor will specifically know you're talking out of your ass. 

You need to do your research here especially, and be very careful about your statement. Don't be stupid, generally. But no, I don't think the answer is any different still, it's just a more careful balancing act. Go for it. One of the other questions points towards successful NSF applications, and I find them to be generally good guides. I used my application as the basis for all but one of my personal statements.