1. S. Yordanova, „Fuzzy sets and fuzzy logic for process modeling and control” in Intelligent Control Systems, 1st ed. Sofia, Bulgaria: TUSofia, 2018, ch.4, sec.4.6, pp. 63-80 (in Bulgarian).
2. M. Petrov, A. Taneva, I. Ganchev, „Fuzzy PID controller design in MATLAB environment“, Proceedings of the Int. Conf. Automatics and Informatics, Sofia, 2007, pp.57-61 (in Bulgarian).
3. D. Ivanova, V. Stoianov, “Design of fuzzy PID controllers”, Scientificpapers of University of Ruse, vol. 48, no. 3.1, pp.114-122 (in Bulgarian).
4. A. Marinchev, „Application of modern algorithms for level control with LabVIEW“, Proceedings of the TU-Sofia, Vol. 66, Issue 2, 2016, pp.205-212 (in Bulgarian).
5. M. Hadjiski, K. Velev, G. Sotirov, I. Kalaykov, „Modern methods and algorithms for control” in Automation of Process Industry. Methods and Algorithms for Control, 1st ed. Sofia, Bulgaria, Tehnika, 1992, ch.6, sec.6.3, pp. 273-306 (in Bulgarian).