Let D =(X,B) be a 4-(v,6,λ) design,and G Aut(D) act block-transtively on D,where X = GF(q) ∪ {∞} and GF(q) a finite field of order q.If G = PSL(2,q),then there exist 4-(12,6,4) designs;if G = PGL(2,q),then there exist 4-(12,6,8),4-(18,6,24) and 4-(33...