Foundations of Mathematics. Pergamon. In this text, S refers to the Peanoaxioms. Holmes, Randall, 1998. Elementary Set Theory with a Universal Set. Academia-Bruylant
Foundations of Mathematics. Pergamon. Uses natural deduction to rederive Peano's axioms from the Grundgesetze system, recast in modern notation. Hill, C. O
S-expressions can be defined by a set of formal inductive axioms analogous to the Peano postulates used to define natural numbers. John McCarthy. History