Axiom:Axiom of Infinity/Class Theory/Formulation 3/Historical Note

Historical Note on Formulation 3 of the Axiom of Infinity (Class Theory)
and introduce this formulation of the Axiom of Infinity in their  of $2010$ as:
 * something rather amusing.

It would not normally be expected that this formulation be used as the basis of serious work in this field of mathematics.