ChatGTP was launched by OpenAI in November 2022
How to Cite AI Generated Content - Artificial Intelligence (AI) - Research Guides at Purdue University Libraries (Note that the guide doesn't have Harvard, but general information is still highly useful.)
SOAS Guidance on Acknowledging and Referencing Generative AI (Artificial Intelligence) This pdf document provided by the Student Learning Centre's page on Generative AI Guidance on Sharepoint.