[F 1] Z. FROLÍK: 
Generalizations of compact and Lindelöf spaces. (Russian with English summary), Czech. Math. Journ. 9 (84) (1959), 172-217. 
MR 0105075[F 2] Z. FROLÍK: 
Generalization of the $G_{\delta }$- property of complete metric spaces. Czech Math. Journ. 10 (85) (1960), 359-379. 
MR 0116305[F 2] Z. FROLÍK: 
On $G_{\delta }$- spaces. Czech. Math. Journ. 9 (84) (1959), 63-65. 
MR 0112116[F 3] Z. FROLÍK: 
Invariance of $G_{\delta }$- spaces under mappings. To appear in Czech. Math. J. 
MR 0126251[F 4] Z. FROLÍK: Complete families of functions. To appear in Czech. Math. J.
[F 5] Z. FROLÍK: 
Relations of completeness. To appear in Czech. Math. J. 
MR 0148029[F 6] Z. FROLÍK: Internal characterizations of complete spaces. To appear in Czech. Math. J.
[F 7] Z. FROLÍK: 
Locally $G_{\delta }$- spaces. To appear in Czech. Math. J. 
MR 0148028[K 1] M. KATĚTOV: 
Über $H$-abgeschlossene und bicompakte Räume. Čas. pěst. mat. fys. 69 (1940), 36-49. 
MR 0001912[K 2] M. KATĚTOV: Remarks on characters and pseudocharacters. CMUC 1, 1 (1960).