In the sciences there exists mathematical functions that are named after the British mathematician George Green.
People refer to them in various ways such as:
Green's function, Green's functions,
Green function, Green functions.
To me, Green's functions, suggests that he (Green) tested and investigated each and every one of these functions one way or the other. Doesn't Green functions sound much better? I.e. that these functions are related to work originally done or started by George Green.
For example, here is a little part from the wikipedia page about these functions
In mathematics, a Green's function is the...
A Green's function sounds so wrong to my ears.
How should it be for singular and plural form?