Kawauchi 2012, Theorem 11.5.3, p. 150. Kawauchi credits this result to Kondo, H. (1979), "Knots of unknotting number 1 and their Alexander polynomials", Osaka J. Math. 16: 551-559, and to Sakai, T. (1977), "A remark on the Alexander polynomials of knots", Math. Sem. Notes Kobe Univ. 5: 451~456. Kawauchi, Akio (2012) [1996]. A Survey of Knot Theory. Birkhäuser. ISBN978-3-0348-9227-8. (covers several different approaches, explains relations between different versions of the Alexander polynomial)
Kawauchi 2012, symmetry section. Kawauchi, Akio (2012) [1996]. A Survey of Knot Theory. Birkhäuser. ISBN978-3-0348-9227-8. (covers several different approaches, explains relations between different versions of the Alexander polynomial)
Fox 1961. Fox, Ralph (1961). "A quick trip through knot theory". In Fort, M.K. (ed.). Proceedings of the University of Georgia Topology Institute. Englewood Cliffs. N. J.: Prentice-Hall. pp. 120–167. OCLC73203715.