Palindromy and ambiguous ideals revisited

The purpose of this article is to revisit the relationship between ambiguou s ideals and palindromy in the simple continued Fraction expansions of quad ratic irrationals begun by the first author and A. J. van der Poorten (1995 , Bull. Austral. Math. Sec. 51, 215-233). We present simpler proofs of know n results, new interrelationships, and correct some misinterpretations. We do this via the infrastructure of real quadratic fields. The conclusion is that palindromy is ambiguity, when properly viewed. (C) 1999 Academic Press .