Біленький, А. Я., and О. Г. Кучер. “CONTRAST CRITERIA OF SYMMETRIC SYSTEMS OF WALSH FUNCTIONS”. Proceedings of National Aviation University (archive) 15, no. 4 (April 5, 2021): 105–114. Accessed April 30, 2026. http://jrnl.kai.edu.ua/index.php/visnik/article/view/15296.