When using Green Open Access literature, the distinction between a preprint and a postprint is very important. While the definitions can vary, "preprints are all the versions of an academic article or other publication before it has been submitted for peer review, while the postprint is the form of the article after all the peer review changes are in place. One can further differentiate between author’s manuscript – the last version which authors send before publication – and publisher’s version which is also called version of record."

Always ask your instructor whether preprint, or even postprint, versions of articles are acceptable for your assignments.