“There was laughter back of the theater, leading to the belief that somebody was telling jokes”

The playwright and drama critic George S. Kaufman (1889-1961) has been credited with saying this about an unsuccessful comedic play:
 
“There was laughter in the back of the theater, leading to the belief that somebody was telling jokes back there.”
 
Kaufman was credited with the line by New York City entertainment columnist Earl Wilson in 1946.
 
   
Wikipedia: George S. Kaufman
George Simon Kaufman (November 16, 1889 – June 2, 1961) was an American playwright, theatre director and producer, humorist, and drama critic. In addition to comedies and political satire, he wrote several musicals, notably for the Marx Brothers. One play and one musical that he wrote won the Pulitzer Prize for Drama: You Can’t Take It With You (1937, with Moss Hart), and Of Thee I Sing (1932, with Morrie Ryskind and Ira Gershwin). He also won the Tony Award as a Director, for the musical Guys and Dolls.
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Of one unsuccessful comedy he wrote, “There was laughter at the back of the theatre, leading to the belief that someone was telling jokes back there.”
     
Old Fulton NY Post Cards
15 July 1946, New York (NY) Post, “It Happened Last Night” by Earl Wilson, pg. 24, col. 1:
Henry Manckiewicz was remembering when George S. Kaufman, reviewing a particularly dreary “comedy” on Broadway, let it have both barrels, then added, “There was laughter in the back of the house, leading to the belief that somebody was telling jokes back there.”
   
Google News Archive
6 July 1952, Miami (FL) Daily News, “George Kaufman ‘Most Unpopular’” by Earl Wilson, pg. 8B, col. 1:
As a critic, he once panned a comedy this way: “There was laughter in the back of the theater, leading to the belief that somebody was telling jokes back there.”
 
Google Books
George S. Kaufman:
An intimate portrait
By Howard Teichmann
New York, NY: Atheneum
1972
Pg. 34:
“There was laughter in the back of the theatre,” one of his reviews began, “leading to the belief that someone was telling jokes back there.”
 
Playbill.com
Of He She Sings: Anne Kaufman Schneider Protects George S. Kaufman’s Legacy
By Mervyn Rothstein
04 Feb 2011
Kaufman was known for his one-liners. Once, when he reviewed a comedy, he wrote, “There was laughter in the back of the theatre, leading to the belief that someone was telling jokes back there.” He said that Skylark, a play starring Gertrude Lawrence, “is a bad play saved by a bad performance.” He once sent a telegram to an actor he disapproved of: “Saw your performance tonight from back of house. Wish you were here.”