The two orientations used to study knuckle-ball effects. Also

An experimental study of Wiffle ball aerodynamics

What are the advantages and disadvantages of using the knuckleball as a primary pitch in baseball? - Quora

Predicting a Baseball's Path

Wind-tunnel experimental drag coefficient results for the Brazuca and

PDF) Aerodynamics of a knuckleball

Takeshi ASAI, Prof., Doctor of Engineering, University of Tsukuba, Tsukuba, Faculty of Health and Sport Sciences

At least the Brazuca soccer ball is ready for the 2014 FIFA World Cup - Los Angeles Times

John GOFF, Professor of Physics, PhD, Physics

Effect of panel shape of soccer ball on its flight characteristics

PDF) A comparison of Jabulani and Brazuca non-spin aerodynamics

Dynamical chaos in a simple model of a knuckleball - ScienceDirect

Applied Sciences, Free Full-Text

A new take on why a knuckleball is so hard to hit - The Washington Post