[1] Arhangel'skii A.V.: Factor mappings of metric spaces. Soviet Math. Dokl. 5 (1965), 368-371.
[2] Arhangel'skii A.V.: On a class of spaces containing all metric spaces and all locally bicompact spaces. Amer. Math. Soc. Transl. 92 (1970), 1-39.
[3] Burke D.K.: 
On p-spaces and $w\Delta$-spaces. Pacific J. Math. 35 (1972), 285-296. 
MR 0278255[4] Burke D.K.: 
Covering properties. Chapter 9, in Handbook of Set Theoretic Topology; K. Kunen and J.E. Vaughan, Eds., North Holland, Amsterdam, 1984. 
MR 0776628 | 
Zbl 0569.54022[5] Burke D.K., Michael E.: 
On certain point-countable covers. Pacific J. Math. 64 (1976), 79-92. 
MR 0467687 | 
Zbl 0341.54022[9] Gillman L., Jerison M.: 
Rings of Continuous Functions. D. Van Nostrand, Princeton, N.J., 1960. 
MR 0116199 | 
Zbl 0327.46040[10] Gruenhage G., Michael E., Tanaka Y.: 
Spaces determined by point-countable covers. Pacific J. Math. 113 (1984), 303-332. 
MR 0749538 | 
Zbl 0561.54016[11] Heath R.W.: 
On open mappings and certain spaces satisfying the first countability axiom. Fund. Math. 57 (1965), 91-96. 
MR 0179763 | 
Zbl 0134.41802[12] Li J., Lin S.: $k_{ømega}$-spaces and Y. Tanaka's question. Acta Math. Hungar. 100 (2003), 321-323.
[13] Martin H.W.: 
Remarks on the Nagata-Smirnov metrization theorem. Topology Proceedings of the Memphis State Univ. Conference, edited by S.P. Franklin and B.V. Smith Thomas, Lecture Note in Pure and Applied Math. 24, pp.217-224, Dekker, 1976. 
MR 0433401 | 
Zbl 0353.54018[14] Michael E.: 
$\aleph_{0}$-spaces. J. Math. Mech. 15 (1966), 983-1002. 
MR 0206907[16] O'Mera P.: 
On paracompactness in function spaces with the compact-open topology. Proc. Amer. Math. Soc. 29 (1971), 183-189. 
MR 0276919[17] Stone A.H.: 
Metrizability of unions of spaces. Proc. Amer. Math. Soc. 10 (1959), 361-366. 
MR 0105672[18] Tanaka Y.: 
On open finite-to-one maps. Bull. Tokyo Gakugei Univ. Ser. IV 25 (1973), 1-13. 
MR 0346730 | 
Zbl 0355.54008[19] Tanaka Y.: 
Some necessary conditions for products of $k$-spaces. Bull. Tokyo Gakugei Univ. Ser. IV 30 (1978), 1-16. 
MR 0512222 | 
Zbl 0427.54016[20] Tanaka Y.: 
Point-countable $k$-systems and products of $k$-spaces. Pacific J. Math. 101 (1982), 199-208. 
MR 0671852 | 
Zbl 0498.54023[21] Tanaka Y.: 
Metrizability of certain point-countable unions. Sci. Math. Jpn. 57 (2003), 201-206. 
MR 1959977 | 
Zbl 1032.54017[22] Tanaka Y.: 
Products of $k$-spaces, and questions. Comment. Math. Univ. Carolinae 44 (2003), 335-345. 
MR 2026168 | 
Zbl 1100.54006[23] Tanaka Y., Zhoh Hao-xuan: 
Spaces determined by metric subsets, and their character. Questions Answers Gen. Topology 3 (1985/86), 145-160. 
MR 0826985[24] Yoshioka I.: 
On the metrizability of $\gamma$-spaces and $ks$-spaces. Questions Answers Gen. Topology 19 (2001), 55-72. 
MR 1815346