http://www.blairenglish.com/exercises/emails/exercises/how_to_disagree_in_email/how_to_disagree_in_email.html#:~:text=When%20writing%20an%20email%2Fletter%20of%20disagreement%2C%20you%20not%20only,reason%20why%20it%20is%20wrong.
https://autoklose.com/how-to-end-an-email/#1-1-degrees-of-gratitude-