Comments on spin operators and spin-polarization states of 2 + 1 fermions S. P. Gavrilov, D. M. Gitman and J. L. Tomazelli Eur. Phys. J. C, 39 2 (2005) 245-248 Published online: 15 February 2005 DOI: 10.1140/epjc/s2004-02026-9