### Description add eq. 7.16a-7.21 ### Acceptance Criteria - [x] Add the formula to the code - [x] Add latex expression to the formula - [x] Add unittests - [x] Add docstrings - [x] Update table in docs with classnames ### Dependencies _No response_ ### Confirmation - [x] I have checked that this feature does not already exist in the issue tracker. - [x] I have read and understood the contribution guidelines.