Unit indices of some imaginary composite quadratic fields. II
[For Part I, cf. Pac. J. Math. 164, 87-104 (1994; Zbl 0796.11049).] Let \(K\) be an imaginary abelian number field of type \((2, 2, 2, 2)\) containing the 8-th cyclotomic field \(\mathbb{Q} (\sqrt {-1}, \sqrt {2})\). Using the fundamental units of real quadratic subfields of \(K\), we give a necessary and sufficient condition for the unit index \(Q_K\) of \(K\) to be equal to 2.
scientific article; zbMATH DE number 910278