  This paper concerns the density of the Hartman--Watson law. Yor (1980)
obtained an integral formula that gives a closed-form expression of the
Hartman--Watson density. In this paper, based on Yor's formula, we provide
alternative integral representations for the density. As an immediate
application, we recover in part a Dufresne's result (2001) that exhibits
remarkably simple representations for the laws of exponential additive
functionals of Brownian motion.
