RBE2_RBE3_common nodes technique

Hello,

I have a request for everyone here. I need some documentation on the connection between 2 parts using RBE2, RBE3. I need first some general info on the 2 types of connections, and any other types of connection for Optistruct (without any contacts) used to tie 2 different parts, maybe 2 parts meshed with different kinds of elements.

Thank you very much !!