Blood group antigens Rb(a), Tr(a), and Wd(a) are located in the third ectoplasmic loop of erythroid band 3.
Jarolim P, Murray JL, Rubin HL, Smart E, Moulds JM. Blood group antigens Rb(a), Tr(a), and Wd(a) are located in the third ectoplasmic loop of erythroid band 3. Transfusion. 1997 Jun; 37(6):607-15.