Laplace approximation

Hi All,

I am confused about the differences between PQL and Laplace
approximations to GLMM (after all, Breslow and Calyton's `PQL paper'
seems to describe a Laplace approximation). If anyone could point me to
a review paper that summarises the literature on these approximations,
and ideally their history, I would be very grateful.

Cheers,

Jarrod