Complex sentence: Criteria for research doctorates vary, but typically include completing a substantial body of original research which may take the form of a single thesis or dissertation, or of a portfolio of shorter project reports (thesis by publication).
Split into simpler sentences: Criteria for research doctorates vary, but typically include completing a substantial body of original research. This may take the form of a single thesis or dissertation, or of a portfolio of shorter project reports (thesis by publication).