PV Performance Model Documentation

I am trying to understand the PV performance model in SAM and I would like to read the references. But I found that two references I am interested in are not available to link from the publication in SAM website.

SAM uses several performance models for PV systems. The possibilities are:

PVWatts
CEC Module
Sandia Module
Simple Efficiency Module
Sandia Inverter
Single Point Efficiency Inverter

SAM's Module page displays a link to documents describing the CEC and Sandia module models. You can find references with links to documentation of the other models in the Help system, either in the References topic, or in the Module and Inverter topics. The simple efficiency module model and single-point efficiency inverter model's are described in the Module topic and Inverter topic, respectively.