Twisting symmetry-spins of pretzel knots (Q803591)

2-knots in \(S^ 4\) may have groups with finite commutator subgroups of the form \(G\times {\mathbb{Z}}_ d\) [\textit{J. A. Hillman}, Bull. Austral. Math. Soc. 16, 449-462 (1977; Zbl 0352.57011)]. The author constructs fibred 2-knots where \(G=Q(8)\) is the quaternion group, and \(d=3,21,27\), extending the range of known examples. They are obtained as products of symmetry- and twist-spinnings of pretzel knots.