Oborskii, G. A., V. I. Koval’kov, V. N. Tikhenko, and P. T. Slobodyanik. “LED Electric-Measuring Indicators for Multithreshold Comparators”. Technology and Design in Electronic Equipment, no. 5, Oct. 2012, pp. 8-13, http://www.tkea.com.ua/index.php/journal/article/view/TKEA2012.5.08.