Editing Sheffer stroke (section)

==History==
The stroke is named after [[Henry Maurice Sheffer]], who in 1913 published a paper in the ''[[Transactions of the American Mathematical Society]]''<ref name="Sheffer_1913"/> providing an axiomatization of [[Boolean algebra (structure)|Boolean algebra]]s using the stroke, and proved its equivalence to a standard formulation thereof by [[Edward Vermilye Huntington|Huntington]] employing the familiar operators of [[propositional logic]] ([[logical conjunction|AND]], [[logical disjunction|OR]], [[negation|NOT]]). Because of self-[[duality (order theory)|duality]] of Boolean algebras, Sheffer's axioms are equally valid for either of the NAND or NOR operations in place of the stroke. Sheffer interpreted the stroke as a sign for nondisjunction ([[logical NOR|NOR]]) in his paper, mentioning non-conjunction only in a footnote and without a special sign for it. It was [[Jean Nicod]] who first used the stroke as a sign for non-conjunction (NAND) in a paper of 1917 and which has since become current practice.<ref name="Nicod_1917"/><ref name="Church_1956"/> Russell and Whitehead used the Sheffer stroke in the 1927 second edition of ''[[Principia Mathematica]]'' and suggested it as a replacement for the "OR" and "NOT" operations of the first edition.

[[Charles Sanders Peirce]] (1880) had discovered the [[functional completeness]] of NAND or NOR more than 30 years earlier, using the term ''[[ampheck]]'' (for 'cutting both ways'), but he never published his finding. Two years before Sheffer, {{ill|Edward Stamm|pl|Edward Bronisław Stamm}} also described the NAND and NOR operators and showed that the other Boolean operations could be expressed by it.<ref name="Stamm_1911"/>