Vacuum polarization in muonic atoms: the Lamb shift at low and medium Z S. G. Karshenboim, V. G. Ivanov and E. Yu. Korzinin Eur. Phys. J. D, 39 3 (2006) 351-358 Published online: 15 June 2006 DOI: 10.1140/epjd/e2006-00133-0