The Gram determinant of type A was introduced by Lickorish in his work on
invariants of 3 - manifolds. We generalize the theory of the Gram determinant
of type A by evaluating, in the annulus, a bilinear form of non-intersecting
connections in the disc. The main result provides a closed formula for this
Gram determinant. We conclude the paper by discussing Chen's conjecture about
the Gram determinant of type Mb evaluated in the Klein bottle.Comment: 17 pages, 19 figure