When referred to journal publications, in 'previous work of Newton on gravity' or 'previous works of Newton on gravity', which one is correct?
You can certainly use both. Newton's previous work includes all of his previous works, and in addition his unpublished things and effort.
In the context of scientists and artists,
- uncountable work is all of the labour, including experiments, sketches, time spent thinking, and all the books, paintings etc, whether published, unpublished, finished or unfinished.
- countable singular work is a given book, painting etc
- countable plural works is all of the books, paintings etc
The countable form is most often used for larger self-contained things such as books, films, journals, paintings etc, and not so often for smaller things such as journal articles, but it's a style question and you will see certainly see it, for example
Chicago Manual of Style: When quoted in text or listed in a bibliography, titles of books, journals, plays, and other freestanding works are italicized; titles of articles, chapters, and other shorter works are set in roman and enclosed in quotation marks.
Remember of course there are very many other meanings of "work", in countable and uncountable forms.