Unitary subgroup of integral group rings.
Let A be a finite abelian group and G = A x 〈b〉, b = 1, a = a, ∀a ∈ A. We find generators up to finite index of the unitary subgroup of ZG. In fact, the generators are the bicyclic units. For an arbitrary group G, let B(ZG) denote the group generated by the bicyclic units. We classify groups G such that B(ZG) is unitary.