(Corrects March 3 story to say Russia is one of the biggest gold producers, not the third biggest, removes line about commercial significance of LBMA membership and changes to say LBMA revoked membership of three Russian banks, not two) By Peter Hobson LONDON (Reuters) -The London Bullion Market Association (LBMA) told Reuters it has asked six Russian gold refiners it accredits if they have commercial links with sanctioned Russian entities and that such links, if found, could affect their accreditation. Governments including those of the United States and the European Union have imposed sancti…