A. Hellen, R. Kalyanaraman,. “M/M/2 Heterogeneous Server Queue With Variant Breakdown and With Discouraged Arrivals”. Mathematical Statistician and Engineering Applications 71, no. 4 (August 30, 2022): 1447–1458. Accessed May 3, 2024. https://www.philstat.org/index.php/MSEA/article/view/641.