Pinning of size-selected Co clusters on highly ordered pyrolytic graphite S. Vučković, J. Samela, K. Nordlund and V. N. Popok Eur. Phys. J. D, 52 1-3 (2009) 107-110 Published online: 06 March 2009 DOI: 10.1140/epjd/e2009-00065-1