« Geography and climate of Singapore » (voir la liste des auteurs). (en) CIA World Factbook: Singapore (en) LibraryofCongressCountryStudies: Singapore Sur
Association, 2010. (en) Bulgaria Country Profile [PDF], LibraryofCongressCountryStudies, 2006. (en) FAO, Tobacco production country rank [4], World Steel Association
associés au sein du Kominform. LibraryofCongressCountryStudies Appendix B – Germany (East). LibraryofCongress, CountryStudies, Hungary, Chapter 3 Economic