Noumba Um, P. (2004). A model for calculating interconnection costs in telecommunications. World Bank : PPIAF.
Чикаго стиль цитування (17-те видання)Noumba Um, Paul. A Model for Calculating Interconnection Costs in Telecommunications. Washington, D.C.: World Bank : PPIAF, 2004.
Стиль цитування MLA (9-ме видання)Noumba Um, Paul. A Model for Calculating Interconnection Costs in Telecommunications. World Bank : PPIAF, 2004.