[1] A. Arhangelskii: 
Some types of factor mappings and the relation between classes of topological spaces. Soviet Math. Dokl. 4 (1963), 1726-1729. 
MR 0158362[6] O. Hájek: 
Notes on quotient maps. Comment. Math. Univ. Carolina 7 (1966), 319-323. 
MR 0202118[7] S. Leader, S. Baron: 
Sequential topologies. Amer. Math. Monthly 73 (1966), 677-678 (problem # 5299). 
MR 1533877[10] F. Siwiec: KM-spaces and km-covering mappings. to appear.