  We confirm the claim of Ref. [D.R. Phillips, C. Schat, Phys. Rev. C88 (2013)
3, 034002] that 20 operators are sufficient to represent the most general local
isospin-invariant three-nucleon force and derive explicit relations between the
two sets of operators suggested in Refs. [D.R. Phillips, C. Schat, Phys. Rev.
C88 (2013) 3, 034002] and [H. Krebs, A.M. Gasparyan, E. Epelbaum, Phys.Rev. C87
(2013) 5, 054007]. We use the set of 20 operators to discuss the chiral
expansion of the long- and intermediate-range parts of the three-nucleon force
up to next-to-next-to-next-to-next-to-leading order in the standard formulation
without explicit Delta(1232) degrees of freedom. We also address implications
of the large-N_c expansion in QCD for the size of the various three-nucleon
force contributions.
