Help for this page
S := A \in A => A \in S
S \in S => S \in S
R \notin R => R \in R
S := (A = S | A \in A) => A \in S or S := (A != S & A \in A) => A \in S R := (A = R | A \notin A) => A \in R or R := (A != R & A \notin A) => A \in R