Ufer, Stefan; Kaiser, Anna; Niklas, Frank; Gabler, Laura (2024): I have three more than you, you have three less than me? Levels of flexibility in dealing with additive situations. Frontiers in Education, 9: 1340322. ISSN 2504-284X
Mu, Jin; Bayrak, Aslihan; Ufer, Stefan (2022): Conceptualizing and measuring instructional quality in mathematics education: A systematic literature review. Frontiers in Education, 7. ISSN 2504-284X