page 14, "Records" by Paul Krassner:

Then Frank Zappa, the astute and knowledgable leader of the Mothers of Invention, told me what was happening : "'Have You Seen Your Mother' wasn't such a bad song. It seemed to me to be the best way of saying something about a certain situation common in contemporary society. It's a pity that that was the only way the Stones could say it, but we've gone so far down that it was the only effective way; it was a good statement." Although Zappa hasn't changed my mind about that particular song (I still maintain that it is a piece of musical garbage), I can see his point.

page 36, "West Coast Music" by Aaren W. Howard

By now, everybody must have heard of the Mothers of Invention, freaks of the recording world. They head a small but highly vocal school of rock-freak-spew-flower spurt music. At this time, a new album has been released in New York called "Absolutely Free", but is not available for review by deadline. The Mothers are a surprisingly musical group and it will be interesting to see where they go on their new album.

Source: archive.org

When I talked to Zappa, he was in a bad mood, constantly castigating everything in American society. Zappa is an almost frighteningly earnest person; his concern over what’s happening all over the place result in a harsh bitterness easily misunderstood for irresponsibility (read more)

Source: Montreal Underground Origins, Charles Ulrich, Javier Marcote