Uniqueness of MV-algebra implication and de Morgan negation

It is shown that the implication of an MV-algebra is determined by de Morgan negation operations on a family of quotients of the given algebra; these quotients may be taken to be totally ordered. Certain existing results on the uniqueness of an MV-algebra implication are thereby elucidated and new criteria for uniqueness derived. These rely on a characterisation of chains on which a de Morgan negation is necessarily unique.