Citation styles ...

1. There are incredibly many. There is not one standard that is used across all disciplines or even within one discipline.

2. Many professors have a preferred style. Search on the website of their chair / department / ..., or ask for it. If there is one: Keep to the specifications of your profs!

3. If you can choose freely, stick to the decision you made. (You can use APA style, Harvard style, etc. as a guideline).

3 facts and 3 questions while waiting for your profs

Example: APA Style

Which citation style do you use?