General ⇒ natbib and acm_proc_article - no reference enumeration

[seson]

Hi all,

I have to use the document class for an acm article, but I'd like to use natbib, too. However, all references at the end of my paper are listed without preceeding numbers. Instead of "[1] author, title", there is just "author, title".

How can I fix that?

References inside the text are fine though (caused by \cite{abc}). It's only the bibliography section that isn't right.

Sebastian