gam.exact is an S-PLUS function which takes a gam
object and produces exact standard errors for each linear term in the
gam call (except for the intercept).
A reference for the software is Dominici F, McDermott A, Hastie TJ
(2004). "Improved Semi-Parametric Time Series Models of Air Pollution
and Mortality,"
Journal of American Statistical Association, 468, 938-948.