Countable Covers of Spaces by Migrant Sets
The motivation for this note is a paper by Hidenori Tanaka in which he shows that the Pixley-Roy hyperspace of a metric space X is normal if and only if X is an almost strong q-set.
Balogh, Zoltan; Mashburn, Joe; and Nyikos, Peter, "Countable Covers of Spaces by Migrant Sets" (1989). Mathematics Faculty Publications. 29.