On free subgroups of units in quaternion algebras II

Abstract

Abstract. Let A ⊆ Q be any subring. We extend our earlier results on unit groups of the standard quaternion algebra H(A) to units of certain rings of generalized quaternions, where a, b ∈ A. Next we show that there is an algebra embedding of the ring H(A, a, b) into the algebra of standard Cayley numbers over A. Using this embedding we answer a question asked in the first part of this paper.