Baseball's Parallax Effect - Check Swing Angles Prove Deceptive
Baseball's most basic motion isn't even defined in the rules, and
Overthinking It: Bill James, Base Umpires, and the Sabermetric
What defines a check swing in baseball? - Quora
Austin weighing street-level light rail in new Project Connect
What If All Checked Swings Were Just Balls? - by Sam Miller
Checked swing - Wikipedia
Overthinking It: Bill James, Base Umpires, and the Sabermetric
Reality of Calling a Checked Swing