They need to be aware of their own self-plagiarism. They need to cite their work.
Is it OK to cite a master’s thesis?
There were 5 answers. You are able to reference their work in your text as long as you make clear in the bibliography what type of document it is.
Can I apply for PhD without masters thesis?
There are extra requirements for students who didn’t complete a thesis in D. programs. A stone/directed project with elements of a thesis is fine with others. Students who did not complete a thesis may be asked to take the GRE for admission.