A sham-controlled, phase II trial of transcranial direct current stimulation for the treatment of central pain in traumatic spinal cord injury. - Fregni,F.; Boggio,PS.; Lima,MC.; Ferreira,MJ.; Wagner,T.; Rigonatti,SP.; Castro,AW.; Souza,DR.; Riberto,M.; Freedman,SD.; Nitsche,MA.; Pascual-Leone,A. (Pain, 2006)