Owego, D. O., and N. B. Okelo. “RELATIONSHIP BETWEEN THE CLASSICAL NUMERICAL RANGE AND ESSENTIAL NUMERICAL RANGES”. IJRDO -JOURNAL OF MATHEMATICS 1, no. 5 (September 30, 2015): 46-53. Accessed May 19, 2024. https://ijrdo.org/index.php/m/article/view/2413.