delta system lemma

If $S$ is a set of finite sets such that $|S|={\mathrm{\aleph }}_1$ then there is a $S^{\prime }\subseteq S$ such that $|S^{\prime }|={\mathrm{\aleph }}_1$ and $S$ is a http://planetmath.org/node/DeltaSystem$\mathrm{\Delta }$-system.

Title	delta system lemma
Canonical name	DeltaSystemLemma
Date of creation	2013-03-22 12:55:00
Last modified on	2013-03-22 12:55:00
Owner	Henry (455)
Last modified by	Henry (455)
Numerical id	6
Author	Henry (455)
Entry type	Theorem
Classification	msc 03E99
Related topic	DeltaSystem