Conversation so far:
What is most important about Hume's academics?
An Enquiry Concerning Human Understanding and An Enquiry Concerning the Principles of Morals were Hume's greatest literary and philosophical achievements
What were the Principles of Morals?
An Enquiry Concerning the Principles of Morals (EPM) is a book by Scottish enlightenment philosopher David Hume. In it, Hume argues that the foundations of morals lie with sentiment, not reason.
Are there any other parts of the Morals?
The first enquiry is called An Enquiry Concerning Human Understanding

Question: What else did he write?
Self-contained rewrite: What else did David Hume write besides his first and second equiries?