1. E. Artin, Theorie der Zöpfe, Abh. Math. Sem. Univ. Hamburg4, 47–72 (1926).
2. C. Bankwitz, G. Schumann, Über Viergeflechte. Abh. Math. Sem. Univ. Hamburg10, 263–284 (1934).
3. J. S. Birman, Braid, links, and mapping class groups. Ann. Math. Studies, Princeton Univ. Press, Princeton Nr. 7 (1974).
4. M. Boileau,L. Siebenmann, A planar classification of Pretzel knots and Montesinos knots. Prepublications of the Univ. Paris-Sud 80 T 38 (1980).
5. G. Burde, Zur Theorie der Zöpfe. Math. Ann.151, 101–107 (1963).