A link to 'ISIS Map Projection Users Guide' is missing in the docs for TProjection/Projection/ProjectionFactory
In the documentation for the TProjection class, there is a reference to the "ISIS Map Projection Users Guide" which explains the meaning for
all Pvl map projection labels that can be used in a Pvl Mapping group when describing a projection.
I also found references to this document in the ProjectionFactory class as well as the Projection class:
This document needs to be written, so this is a large effort.