References
- Haubrich, H. (1992). International charter on geographical education. Freiburg: Paedagogische Hochschule Freiburg. Retrieved from http://www.igu-cge.org/charters_1.htm.
- Institute of Education Sciences & National Center for Education Statistics. (2014). Program for international student assessment. Washington, DC: National Center for Educational Statistics. Retrieved from http://nces.ed.gov/surveys/pisa/.
- International Association for the Evaluation of Educational Achievement. (2014). International civic and citizenship education study 2016. Amsterdam: IEA Secretariat. Retrieved from http://www.iea.nl/iccs_2016.html.
- Mullis, I.V.S., & Martin M.O., eds. (2013). TIMSS 2015 assessment frameworks. Chestnut Hill, MA: TIMSS & PIRLS International Study Center, Boston College.