Thomas MENKHOFF and Christoph Reichert. "Options and Problems of Comparative Secondary Analyses of Datasets on the Informal Sector - Small-Scale Industries in Ghana and Nigeria (in German)" Empirische Sozialforschung Und Entwicklungsländer, Methodenprobleme Und Praxisbezug, Cologne Studies on Developing Countries, Saarbrücken Vol. 15 (1992)
Available at: http://works.bepress.com/thomas_menkhoff/99/