I only skimmed it too. I came across the Silver reference in Bayesian Methods by Leonard and Hsu, pp249-250. It says Silverman (not Silver) and Leonard have suggested regularizing a density $g$ by minimising things including terms like

$$ \int \left[ \frac{\partial^2 g}{\partial x^2} \right]^2 d x $$

which is quantum-theory-ish.