Oracle Database Discussions

Hello guys,
i readed many documentations about indeces and performance issues. In many cases i could optimize my queries.

But one thing, i didn't find while i was searching for documents.

What value/fact specifies the following:

1) How much branch nodes can a root block contain/handle?
2) How much leaf nodes can a branch node contain/handle?
3) How much values can a leaf node contain/handle?

It there any rule that specifies at which point the branch block / leaf block should be splitted?

Maybe you can give me a link to a documentation about that topic or explain by yourself....
Thanks :-)

Regards
Stefan