I just finished reading Dangerously Funny - David Bianculli's story of the Smothers Brothers and their controversial CBS variety show. One of the sad things about the Smothers show is that it's never shown on TV anymore, and even the recent DVD sets are incomplete "Best Of" packages.
Well, there's always YouTube. Here we have the boys performing "Boil That Cabbage Down" with the Boston Pops on a (presumably PBS) '80s TV special. It's the same song they recently did - in animated form - on an episode of The Simpsons.