Giving credit to the original author by citing sources is the only way to use other people's work without plagiarizing. But there are a number of other reasons to cite sources:
CURRENT CRITERIA FOR A PROPOSAL
A student's proposal details the research that he or she is undertaking, offering a synopsis of the project and detailing the context and scope of the work. The proposal is an important indication of whether the student will manage the challenging task of completing the research and writing it up.
PhD, 8000 to 10000 words
M Ed by dissertation, 6000 to 7000 words
M Ed by coursework and research report, 3000 to 4000 words
B Ed Honours, 1500 to 2000 words
-- Extract from the booklet From application to graduation (Johannesburg: Wits School of Education, 2015)