We wish to estimate the probability density g(y) that produced an obse
rved random sample of vectors y(1), y(2),..., y(n). Estimates of g(y)
are traditionally constructed in two quite different ways: by maximum
likelihood fitting within some parametric family such as the normal or
by nonparametric methods such as kernel density estimation. These two
methods can be combined by putting an exponential family ''through''
a kernel estimator. These are the specially designed exponential famil
ies mentioned in the title. Poisson regression methods play a major ro
le in calculations concerning such families.