## Zentralblatt MATH

Publications of (and about) Paul Erdös

Zbl.No:  285.04002
Autor:  Erdös, Paul; Hajnal, András
Title:  Some remarks on set theory. XI. (In English)
Source:  Fundam. Math. 81, 261-265 (1974).
Review:  The authors solve the following problem: Let |S| = m determine the largest cardinal f(m) so that if A\alpha \subset S, |A\alpha| < m, are subsets of S no one of which contains any other one can always find m of the sets A\alpha whose union has a complement of size \geq f(m). The author determines f(m) for every infinite cardinal m, e.g. f(\aleph0) = \aleph0.
Classif.:  * 04A10 Ordinal and cardinal numbers; generalizations
04A20 Combinatorial set theory

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