  The difference between the guiding center phase-space Lagrangians derived in
[J.W. Burby, J. Squire, and H. Qin, Phys. Plasmas {\bf 20}, 072105 (2013)] and
[F.I. Parra, and I. Calvo, Plasma Phys. Control. Fusion {\bf 53}, 045001
(2011)] is due to a different definition of the guiding center coordinates. In
this brief communication the difference between the guiding center coordinates
is calculated explicitly.
