Here are 3 examples that you can use for resignation letter as Assistant Professor -. Resignation letters should use the formal greeting: "Dear".The first sentence in the letter should state that you are resigning and when. The letter should be signed and attached to a cover e-mail. The date of retirement would normally be the end of either the fall or spring semester. Need to write two weeks notice? Download free nursing resignation letter templates in MS Word, Apple Pages, Google Docs, and PDF formats. Theodore John Kaczynski also known as the Unabomber was an American mathematician and domestic terrorist. "Our country is facing a grave challenge," Freeland wrote in her resignation letter.