Cole’s Law: Thinly sliced cabbage (coleslaw joke)

Arthur Bloch’s 1977 bestseller, Murphy’s law and other reasons why things go wrong, included a food joke: “Cole’s Law: Thinly sliced cabbage.” The coleslaw joke is still told.
 
     
Wikipedia: Coleslaw
Coleslaw, sometimes simply called slaw in some American dialects, is a type of salad consisting primarily of shredded raw cabbage. It may also include shredded carrots.
     
Google Books
7 September 1978, New Scientist, pg. 744, col. 1:
Offered as contenders for the great unshakeable list of indisciplinary laws—Sod’s Law, Newton’s Fourth Law of Mtion, the Inverse Midas Touch and their kin—is a list published in SLAC Beam Line, the broadsheet of the Stanford Linear Accelerator Center. Like all such compendia very few make the appropriate rating. Cole’s Law, described as thinly sliced cabbage, is frankly pretty wet;...
         
Google Books
1,001 logical laws, accurate axioms, profound principles, trusty truisms, homey homilies, colorful corollaries, quotable quotes, and rambunctious ruminations for all walks of life
By John Peers, Gordon Bennett and George Booth
Garden City, NY: Doubleday
1979
Pg. 59:
Cole’s Law: Thinly sliced cabbage.
 
Google Books
Peter’s people
By Laurence J Peter
New York, NY: Tower
1979
Pg. ?:
COLE’S LAW: Grated cabbage.
 
Google Books
3 September 1979, New York magazine, pg. 73, col. 1:
Cole’s Law: Thinly sliced cabbage (courtesy The Official Rules).
 
4 June 1980, Kokomo (IN) Tribune, pg. 1, col. 1:
Today’s Chuckle
Cole’s Law—Thinly sliced cabbage.