Here’s a helfpul chart from Purdue OWL about the big three citation formats.

MLA

• Interactive Practice Template (MLA.org)
• Citations Overview (Purdue OWL)
• Citation Generator (Scribbr)
• Citation Generator (Citation Machine)

APA

• Reference Examples (APA.org)
• Formatting and Style Guide (Purdue OWL)
• Citation Generator (Scribbr)
• Citation Generator (MyBib)

Chicago

• Quick Guide
  • Notes and Bibliography System (literature, history, arts/humanities)
  • Author-Date System (social sciences, sciences)