Electronic structure and correlations of vitamin B12 studied within the Haldane-Anderson impurity model Zafer Kandemir, Selma Mayda and Nejat Bulut Eur. Phys. J. B, 89 5 (2016) 113 Published online: 02 May 2016 DOI: 10.1140/epjb/e2016-60702-x