It is argued with the help of a counter example that recent claims about the uniqueness of a certain division of the total optical field in an inhomogeneous medium into a contribution propagating in one direction and one propagating in the opposite direction are erroneous.
FRANS W. SLUIJTER, "Arbitrariness of Dividing the Total Field in an Optically Inhomogeneous Medium into Direct and Reversed Waves," J. Opt. Soc. Am. 60, 8-9 (1970)