Be and Bn stars: Balmer discontinuity and stellar-class relationshipY. R. Cochetti, J. Zorec, L. S. Cidale, M. L. Arias, Y. Aidelman, A. F. Torres, Y. Frémat and A. GranadaA&A, 634 (2020) A18DOI: https://doi.org/10.1051/0004-6361/201936444