What to read to start writing quality Cover Letters?

Question

Upwork

Good day to all! Can you please tell me what can be read to improve the quality of the Cover Letter and, accordingly, the Proposal conversion in Interview?
Many thanks in advance for the replies!

Answer 1

If you write in php - a php tutorial, if in python - a python tutorial ... Well, you understand.
The best cover letter is a list of things you can do.

Answer 2

For example - https://book.jff.name/part/upwork-cover-letter/

Answer 3

I recommend reading a few books in your area of ​​expertise.