Identification of Three Novel Hb F Variants: Hb F-Hayward [ G γ1(NA1)Gly→Asp, G G T>G A T], Hb F-Chori-I [ A γ T 16(A13)Gly→Asp, G G C>G A C] and Hb F-Chori-II [ A γ I 29(B11)Gly→Glu, G G A>G A A]