A question over the link between materials and substances

Hello everyone,

As we know, the data of substances in EHS module is connected to the data of materials in MM module.

But If one material is a mixture, and it has several components of substances in it. How can I make several substances connected with one material in SAP release 6.0?

And the 2nd question is:

Is that possible to make one substance identified by several UN numbers?

This is my first time to come here. I really hope that somebody could help me.

Thank you in advance !

Best regards,

Li