  In spite of the relevance of the proposal introduced in the recent work A.
Abedi, N. T. Maitra and E. K. U. Gross, J. Chem. Phys. 137, 22A530, 2012, there
is an important ingredient which is missing. Namely, the proof that the norms
of the electronic and nuclear wavefunctions which are the solutions to the
nonlinear equations of motion are preserved by the evolution. To prove the
conservation of these norms is precisely the objective of this Comment.
