Chris L. Swiden (2013), Effects of Challenge-BasedLearning on Student MotivationandAchievement, A professional paper submitted in partial fulfillment of the requirements for the degree of Master of Science in Science Education, Montana State University, Bozeman, Montana, p.9
Johnson, Laurence F.; Smith, Rachel S.; Smythe, J. Troy; Varon, Rachel K. (2009). Challenge-BasedLearning: An Approach for Our Time. Austin, Texas: The New Media Consortium, p. 9