1. Some generalizations of metric spaces;Ceder;Pacific J. Math.,1961
2. General Topology;Engelking,1977
3. Stratifiable spaces are M2;Gruenhage;Topology Proc.,1976
4. On the M3⇒M1 question;Gruenhage;Topology Proc.,1980
5. Stratifiable spaces as subspaces and continuous image of M1-spaces;Heath;Proc. Amer. Math. Soc.,1981