“…Hence, M 3 is a prism manifold, which are characterized by their fundamental group. According to the notation of [23] this is M (2, 1), also called the Quaternionic Space [17]. Consider now the presentation m → (1, 2, 3, 4), c → (1, 4, 3, 2), the fundamental group of M 4 is SL 2 (Z 3 ) ∼ = Z 3 Q 8 .…”