Livesey, M. (2021) Advice on using theory in academic work. Available at: https://www.e-ir.info/2021/03/30/student-feature-advice-on-understanding-theory-in-academic-work/ (Accessed: 7 September, 2021).
Oxford University Press (2021) Very Short Introductions. Available at: https://birmingham-primo.hosted.exlibrisgroup.com/permalink/f/vmc2c6/44BIR_ALMA_DS61183977410004871 (Accessed: 7 September 2021).
Sacred Heart University (2020) Organising academic research papers: theoretical framework. Available at: https://library.sacredheart.edu/c.php?g=29803&p=185919 (Accessed: 7 September, 2021).
This website provides an overview of philosophical periods and movements, as well as individual philosophers. Many theories that you will come across in academia stem from philosophy (e.g. Marxism, Phenomenology, Post-Structuralism etc.):
Mastin, L (2021) The Basics of Philosophy. Available at: https://www.philosophybasics.com/ (Accessed: 7 September, 2021).
If you are studying an Arts subject, and English Literature in particular, you might find the following guide to literary theory helpful:
The Writing Lab & Purdue OWL (2021) Literary theory and schools of criticism. Available at: https://owl.purdue.edu/owl/subject_specific_writing/writing_in_literature/literary_theory_and_schools_of_criticism/index.html (Accessed: 7 September, 2021).