Published online by Cambridge University Press: 26 February 2010
In [5] we have developed part of a theory of K- analytic sets that forms a common generalization of the theory of Lindelöf K- analytic sets developed by Choquet, Sion and Frolik and the theory of metric analytic sets developed by Stone and Hansell. As we explain in [5], this theory parallels the recently developed theory of Frolík and Holický, but has certain advantages. In this paper we take the theory rather further, and, in particular, we prove a number of variants of Lusin's first separation theorem and give some of their applications. We make free use of the definitions, notation and conventions introduced in [5].