1. A.K. Erlang, (1909, 1920), The theory of probabilities and telephone conversations’, and ‘Telephone waiting times’, first published in Nyt Tidsskrift for Matematik, B 20 (1909) 33; Matematisk Tidsskrift, B 31 (1920) 25; E. Brockmeyer, et al., The Life and Works of A.K.Erlang, (English translations of both articles) The Copenhagen Telephone Company, Copenhagen, 1948.
2. Delay probability formulas when the holding times are constant;Crommelin;P.O. Electr. Engr. J.,1932
3. Elementary methods for some waiting time problems;Prabhu;Opns. Res.,1962
4. Queues and Inventories;Prabhu,1965
5. Combinatorial Identities;Riordan,1968