found: Work cat.: The Vestibules. Get spiffy! [SR] 2001:liner notes (what else is one to say about this lengthy collection of sketches ... a comedy group recording some sketches ...)
found: Merriam-Webster(sketch: a slight theatrical piece having a single scene; especially: a comic variety act)
found: Saks, S. Funny business : the craft of comedy writing, c1991:p. 39 (Sketch comedy, which is a broad situation in one scene (probably originated, as much comedy has, from burlesque) is used today mostly in variety shows and revues)
found: Schwarz, L. The craft of writing TV comedy, c1988:p. 103 (So far in this book we have looked at quickies, sketches (short and long) and half-hour comedy format)