a1 Facultad de Ciencias, Universidad de Zaragoza, Spain
a2 Department of Mathematics, University of Warsaw, Poland
Let be a closed 3-braid in S3 with axis Lγ. The exterior of γ U Lγ in S3 is a fibre bundle over S1 with fibre a disc with 3 holes. The monodromy is given by a matrix in PSL(2,) and the braid γ is called hyperbolic if its matrix is hyperbolic.
(Received June 11 1984)
(Revised January 17 1985)