MUST, HAVE TO AND SHOULD

https://myblog-inplainenglish.blogspot.com/2014/02/should-must-or-have-to.html

https://learnenglishteens.britishcouncil.org/grammar/beginner-grammar/have-must-should-obligation-advice

https://www.teachya.com/grammar/intermediate/must_should_have_to.php
https://www.thoughtco.com/must-have-to-and-need-to-in-english-4177288