I am writing a project proposal for the first time but I am in dilemma whether I should add the citation in the abstract as well or not. Any suggestions?
Generally citations are avoided in an abstract. I've seen citations allowed a few times a various conferences - I assume because the abstracts are expected to stand alone i.e., without any accompanying paper - but it isn't the norm (at least in my field). Probably you should ask why you feel like you need them. Is it critical to call out specific prior works? Are you expecting the abstract to be viewed with no other context or material available? Whether or not you add them depends on the guidelines/expectations for the project proposal in the end though.