1. National Population Commission ORC Macro Nigeria Demographic and Health Survey 2003 http://pdf.usaid.gov/pdf_docs/Pnacx579.pdf
2. National Population Commission ICF Macro Nigeria Demographic and Health Survey 2008 http://nigeria.unfpa.org/pdf/nigeriadhs2008.pdf
3. Influence of user fees on contraceptive use in Malawi;Hennink;Afr Popul Stud,2005
4. Willingness to pay for poison control centers;Phillips;J Health Econ,1997