oxygen sensor locations

I own a 2001 Oldsmobile Aurora and have been told that it has 3 O2 sensors in it. I have only founf the one after the Cat. Where are the two is ther is two located I have look around the exhaust header but haven't been able to locate. Are they hidden or are they acessable?

Where can I see a picture of they locations?


Thanks you for your time
Bob

Wrong section bro.

This is for Blazers, not the Aurora.