This is the notation of a source used for a paper

The right answer is citation

This is a reference to the source of information you use to write your paper. This refers to when you use, directly or indirectly, the indispensable elements of someone's else in your work. Direct citations are when you directly cite someone's idea, those are usually between marks and used when you want to make clear the use of an idea of someone's else.

This is called a citation