Citing a reference multiple times I am trying to write an introduction to a grant proposal (not for actual research, but because it is part of an assignment that was given to me as an organic chemistry student). I am trying to reference a paper multiple times, and I was wondering whether or not I am supposed to use the same superscript number that corresponds to the reference I am citing every time I cite the reference in my paper. Do I use the same superscript (or different superscripts) every time I cite the reference, or do I only need to include a citation once?
If you are using a numbered referencing format (rather than an Author,Year format), there should be one numbered entry in your reference list for each individual source you reference.

Use the same superscript throughout the manuscript to refer to that reference; it might appear once or it might appear several times.

The exception to this rule would be if you are in a field that uses footnotes. Footnotes are a different matter entirely.

Ideally, you should get used to using a citation manager even at this early stage, it will make your life much easier now and in the future. Your citation manager will handle a lot of this sort of thing for you once you've learned how to use it.