Gangur, Mikuláš, and Miroslav Plevný. “On the Problem of Generating a Large Number of Comparable Test Variants”. Journal on Efficiency and Responsibility in Education and Science 11, no. 4 (January 9, 2019): 78-84. Accessed January 23, 2019. https://www.eriesjournal.com/index.php/eries/article/view/220.