S is not a set.
Elements in S are not required to be unique in S.
S contains exactly a pair of elements.
Each element in S is represented by a text item.
Element y, in S, is asymmetrically associated with element x, in S, and is next in order from that x, in S. Element X shall be recognized as The First Element in S, and element y shall be recognized as The Last Element in S.
If S is said to contain an element or elements of a given description, and that description is faulty, then S does not contain such elements or such an element.
S does not contain itself.
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