A Remark on Kac-Wakimoto Hierarchies of D-type

For the Kac-Wakimoto hierarchy constructed from the principal vertex operator realization of the basic representation of the affine Lie algebra $D_n^{(1)}$, we compute the coefficients of the corresponding Hirota bilinear equations, and verify the coincidence of these bilinear equations with the ones that are satisfied by Givental’s total descendant potential of the $D_n$ singularity, as conjectured by Givental and Milanov in \cite{GM}