J. M. Imperial et al.,  "UniversalCEFR: Enabling Open Multilingual Research on Language Proficiency Assessment", in Proc. of the 2025 Conf. on Empirical Methods in Natural Language Processing, Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng, Ed., Suzhou, China, Association for Computational Linguistics, 2025, pp. 9714-9766