[11 A. I. BASHKIROV:
On continuous maps of Isbell spaces and strong $0$-dimensionality. Bull. Pol. Acad. Sci. 27, 7 (1979), 605-611.
MR 0581560
[3] R. ENGEIKING: General Topology. Warszawa, 1977.
[5] S. MRÓWKA:
On completely regular spaces. ibid. 41 (1954), 105-106.
MR 0063650