  In a recent paper, Hassoul et al.[1], the authors proposed an analysis of the
quantum dynamics for general time-dependent three coupled oscillators through
an approach based on their decouplement using the unitary transformation
method. Thus, to diagonalize the transformed Hamiltonian, they introduce a new
unitary operator corresponding to a three-dimensional rotation parameterized by
Euler angles. Through this procedure, Hassoul et al. [1] claim that the coupled
oscillatory subsystems are completely decoupled. This last approach is partly
wrong. In this brief note, we show that their method is indeed not correct and
we try to explain what truly lies behind their mistakes. We also propose a
brief discussion on an alternative method that might achieve satisfactory
results.
