Arduino DUE SAM Software Package Documentation

I have found that there is a large number of features for the Arduino Due that are not implemented in the Arduino Core, but are available through the SAM software package located in %APPDATA%\Local\Arduino15\packages\arduino\hardware\sam\1.6.6\system\libsam .

Is there any documentation out there for these functions or a way to auto-generate documentation based on their comments?

I am also trying to find some docs and advices about how to use the libsam features but it still being a mistery for me. Did you find someting usefull about Arduino Due Libsam ?