Axiom:Sigma-Ring Axioms

Definition
Let $\Sigma$ be a system of sets.

Formulation 1
$\Sigma$ satisfies the $\sigma$-ring axioms :

Formulation 2
$\Sigma$ satisfies the $\sigma$-ring axioms :

Also see

 * Definition:Sigma-Ring


 * Equivalence of Definitions of Sigma-Ring