What implementation does classregtree use?

Hi there!

I am wondering what Implementation (e.g. ID3, C4.5, ...) the matlab class classregtree uses to build its decision tree?

Can't find anything in the documentation and nothing in the *.m file. Unfortunately I am not able to figure out what implementation it is from the code.

Any help would be appreciated, I'd be especially happy about a source though ;-)

Thanks, Jay