Comment on `On the Quantum Theory of Molecules' [J. Chem.Phys. {\bf   137}, 22A544 (2012)]
  In our previous paper [J. Chem.Phys. {\bf 137}, 22A544 (2012)] we argued that the Born-Oppenheimer approximation could not be based on an exact transformation of the molecular Schr\"{o}dinger equation. In this Comment we suggest that the fundamental reason for the approximate nature of the Born-Oppenheimer model is the lack of a complete set of functions for the electronic space, and the need to describe the continuous spectrum using spectral projection. 
Brian T Sutcliffe and R Guy Woolley
quant-ph