Puurtinen, Marjana, Markus Nivala, och Arja Virta. ”Visual Sources and Historical Thinking in Higher Education”. Nordidactica. Journal of Humanities and Social Science Education 5, no. 2015:4 (februari 18, 2016): 1–20. åtkomstdatum juni 11, 2025. https://journals.lub.lu.se/nordidactica/article/view/19012.