MALIKOW, F. Singular vectors corresponding to imaginary roots in verma modules over affine Lie algebras. MATHEMATICA SCANDINAVICA, [S. l.], v. 66, p. 73–90, 1990. DOI: 10.7146/math.scand.a-12293. Disponível em: https://www.mscand.dk/article/view/12293. Acesso em: 27 apr. 2024.