Bill Schroeder, Drew Olson, Craig Counsell, Bob Uecker (2016). “If These Walls Could Talk: Milwaukee Brewers: Stories from the Milwaukee Brewers Dugout, Locker Room, and Press Box”, p.45, Triumph Books
Quoted in Sporting News, 7 Aug. 1971. Berra says in The Yogi Book (1998) that he was referring here to the difficulty of playing left field in Yankee Stadium in late autumn when "the shadows would creep up on you and you had a tough time seeing the ball off the bat."