Georgieva, Magdalena, and Verica Bakeva. 2000. “BUSY PERIOD AND NUMBER OF CUSTOMERS SERVED DURING THE BUSY PERIOD IN A \(Geo^X G_D 1\) QUEUEING SYSTEM”. Matematichki Bilten 24 (1): 121-30. https://bilten.smm.org.mk/index.php/bilten/article/view/1651.