Widely Used Citation Styles
- APA (American Psychological Association) – Common in psychology, education, and social sciences.
- MLA (Modern Language Association) – Used in literature, humanities, and language studies.
- Chicago/Turabian – History, arts, publishing; has two systems: Notes & Bibliography (footnotes) and Author–Date.
- Harvard – Popular in the UK, Australia, and international academia; author–date system.
- IEEE (Institute of Electrical and Electronics Engineers) – Engineering, computer science, technical fields.
- AMA (American Medical Association) – Medicine, health sciences.
- ACS (American Chemical Society) – Chemistry.
- CSE (Council of Science Editors) – Biology and natural sciences; citation-name, citation-sequence, or name–year systems.
- Vancouver – Biomedical sciences; numbered referencing.
Specialized or Discipline-Specific Styles
- Bluebook – Law and legal writing in the U.S.
- ALWD (Association of Legal Writing Directors) – Alternative to Bluebook, for legal studies.
- OSCOLA (Oxford Standard for the Citation of Legal Authorities) – Law in the UK and Europe.
- MHRA (Modern Humanities Research Association) – Humanities, especially literature.
- SBL (Society of Biblical Literature) – Religious and theological studies.
- AAA (American Anthropological Association) – Anthropology.
- ASA (American Sociological Association) – Sociology.
- APA 7th (variant) – Expanded edition, also adapted for nursing and education.
Publisher- or Journal-Specific Styles
- Nature – Sciences; numerical style.
- Science – Specific format for research articles.
- Elsevier / Cell Press / Springer / Wiley formats – Journals often mandate their own citation templates.
- ACM (Association for Computing Machinery) – Computer science.
Regional / Institutional Styles
- MHRA (UK-focused humanities style)
- DIN 1505 / ISO 690 (Germany, Europe) – Technical and academic publications.
- Turabian – Simplified Chicago style for students.
Summary:
The “big four” are APA, MLA, Chicago, and Harvard (most recognized worldwide). Disciplines then branch into their own: IEEE for engineering, AMA for medicine, Bluebook for law, ACS for chemistry, Vancouver for health sciences, etc.