a1 University of Nottingham
The braid group on n + 1 strings has the presentation
where xi corresponds to the single crossing of the i string over the i + 1 string, and rij is a commutator when i < j − 1, and a braid relator when i = j − 1. B1 is the trivial group and B2 is infinite cyclic; we shall assume n ≥ 2 throughout.
(Received March 31 1982)