Goetz, T., Pekrun, R., Zirngibl, A., Jullien, S., Kleine, M., Vom Hofe, R., & Blum, W. (2004). Academic achievement and emotions in mathematics: A longitudinal multilevel analysis perspective. Zeitschrift fur Padagogische Psychologie, 18(3-4), 201-212. https://doi.org/10.1024/1010-0652.18.34.201