Siegfried Boecherer, Toshiyuki Kikuta, Sho Takemori. Weights of the mod p kernels of the theta operaters. Canadian Journal of Mathematics. 2018. 70. 2. 241-264
Toshiyuki Kikuta. On the theta operator for Hermitian modular forms of degree 2. Abhandlungen aus dem Mathematischen Seminar der Universitaet Hamburg. 2017. 87. 1. 145-163