Hirofumi Yamada, Toshiharu Sugawara "Tensor products of singular holomorphic representations of $\mathrm{SU}\left( {n,n} \right)$ and $\mathrm{mp}\left( {n,R} \right)$," Proceedings of the Japan Academy, Series A, Mathematical Sciences, Proc. Japan Acad. Ser. A Math. Sci. 58(7), 315-318, (1982)