  Comments to the statements of Srikanth (1999) are presented. As for the
standard definition of the Poynting-Robertson drag, the results of Srikanth
(1999) are incorrect. Srikanth's statements about the isothermality condition
and ``red-shift'' are also discussed. Srikanth's results are generalized for
the most general case of the equation of motion when momentum loss per unit
time is proportional to -v/c (higher orders are neglected), where v is
(heliocentric) velocity of the particle, c is the speed of light.
