Number: 4 The most recent Documentos de Trabajo sobre Economía Regional y Urbana (only in Spanish) - Public hospitals accounts receivable and regional differences in the provision of health services in Colombia Jhorland Ayala-García, Karelys Guzmán-Finol Working Papers on Economics - A Mixed Duopoly in the Provision of Payment Services Carlos Alberto Arango-Arango, Yanneth Rocío Betancourt-García Working Papers on Economics - Distribution, Inequality and Poverty in Colombia: An Assessment of the Contribution of the Minimum Francisco Javier Lasso-Valderrama, Carmiña Ofelia Vargas-Riaño