@inproceedings{robert2020vertex,
title={Vertex algebraic intertwining operators among generalized Verma modules for affine Lie algebras},
author={Robert McRae},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20220415171757647373052},
booktitle={Advances in Mathematics},
volume={374},
pages={107351},
year={2020},
}

Robert McRae. Vertex algebraic intertwining operators among generalized Verma modules for affine Lie algebras. 2020. Vol. 374. In Advances in Mathematics. pp.107351. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20220415171757647373052.