Primary PDF: proceedings.mlr.press/v80/cremer18a/cremer18a.pdf . Title-page byline: Chris Cremer, Xuechen Li and David Duvenaud; PMLR80,1078–1086(2018). Table1 on printed page1079 defines the inference, approximation and amortization gaps; the introduction specifies the optimal per-observation approximation within the chosen family.