Comment on 'Analytical solution of Mori's equation with hyperbolic secant memory'

The hyperbolic secant memory function recently proposed by Tankeshwar and Pathak has been analysed using the recurrence relations formulation. In particular, the relevant Hilbert space structure for this memory function has been deduced and compared with those of others obtained exactly from Hermitian many-body models. The realizability of the proposed memory function in conventional many-body models is further discussed.