We consider the problem of optimally controlling a semi-Markov chain with countable state space and unbounded costs. We assume that a particular control is suspected of being optimal and derive conditions for checking whether this is so. The result is applied to the following queueing system. A...

World Development Report 1997: The State in a Changing World. By the World Bank. New York: Oxford University Press, 1997. Pp.viii + 265. ISBN 0 19 521115 4 and 521114 6 Agenda for Africa's Economic Renewal. Edited by Benno Ndulu and Nicolas van de Walle. New Brunswick and Oxford: Transaction...