I often search Google for programming-related questions I have, and rely heavily on the site:stackoverflow.com filter to restrict results to Stack Overflow posts, for example. In some cases, like working with Excel, multiple sites may have useful content (e.g. Stack Overflow and Superuser).
Is there a way I can return results from two such sites at once, rather than having to run two separate site:-filtered searches?
I have tried |, ,, ;, and OR, both with spaces and without, but have had no luck.