Promoter region sequence differences in the A and G gamma globin genes of Brazilian sickle cell anemia patients oleh C.G. Barbosa, N.J. Goncalves-Santos, S.B. Souza-Ribeiro, J.P. Moura-Neto, D. Takahashi, D.O. Silva, A.F. Hurtado-Guerrero, M.G. Reis, M.S. Goncalves