Switching of vortex polarization in 2D easy-plane magnets by magnetic fields J. P. Zagorodny, Y. Gaididei, F. G. Mertens and A. R. Bishop Eur. Phys. J. B, 31 4 (2003) 471-487 Published online: 06 March 2003 DOI: 10.1140/epjb/e2003-00057-y