Effect of hydroxyurea on mortality and morbidity in adult sickle cell anemia: risks and benefits up to 9 years of treatment. - Steinberg,M.H.; Barton,F.; Castro,O.; Pegelow,C.H.; Ballas,S.K.; Kutlar,A.; Orringer,E.; Bellevue,R.; Olivieri,N.; Eckman,J.; Varma,M.; Ramirez,G.; et al. (Jama, 2003)