All Six Sigma exams require knowledge of the Founding Fathers of Six Sigma and the Quality Movement. Here is a great study guide & reference for you:
Genichi Taguchi contributed several important concepts to the field of quality including the Taguchi Loss Function and Taguchi Robust design.
Joseph M Juran was a quality luminary that focused on top management involvement, the quality trilogy, quality cost measurement, and Pareto analysis.
Walter Shewhart is often referred to as the “Father of Quality Control” – he worked as a process engineer for Western Electric and Bell Labs.
William Edwards Deming was an American management consultant and educator. He popularized the PDCA cycle first developed by Walter Shewhart.