Relationship and Range of RVI in SNAP

Microwave Toolbox
1

@ABraun
I would like to know the exact relationship and range for the RVI that is implemented in SNAP.
RVI

The expression proposed by Kim and van Zyl 2009 is,

RVI_Kim

However, many other papers propose the RVI as,
RVI1

or

RVImin

I would like to know which one of these relationships is implemented in SNAP.