Cặp được sắp

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Năm 1921, Kazimierz Kuratowski đưa ra định nghĩa sau về cặp được sắp (a, b):[1][2]

Chú thích[sửa | sửa mã nguồn]

  1. ^ cf introduction to Wiener's paper in van Heijenoort 1967:224. van Heijenoort observes that the resulting set that represents the ordered pair "has a type higher by 2 than the elements (when they are of the same type)"; he offers references that show how, under certain circumstances, the type can be reduced to 1 or 0.
  2. ^ Kuratowski, Casimir (1921). “Sur la notion de l'ordre dans la Théorie des Ensembles” (PDF). Fundamenta Mathematicae 2 (1): 161–171.