Blatt, H. P., R. Grothmann, and R. K. Kovacheva. “Sign Changes in Rational Lw1-Approximation”. Ukrains’kyi Matematychnyi Zhurnal 58, no. 2 (February 25, 2006): 283–287. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3452.