I've tried that [before], but with multiple parameters, I simply got zero results. I then enclosed the site:foo OR site:bar within parentheses, leaving the rest of the query outside parentheses. Whichever site:foo came first would be matched, but only it appeared to be matched. Subsequent site:bar, etc. parameters did not produce any matches in the results.

I'll have a look at your links, in a minute -- probably should have done that first.

EDIT: Well, your second link sure works. I wonder what I was doing wrong. When I saw someone else('s or s') comments online to the effect that it didn't work, I assumed that was why my own experience failed.

I'm in serious need of some coffee, at the moment. Thanks for correcting my mis-impression; I look forward to straightening it out in my mind and taking advantage of this feature.