References for notebooks on GPs with Uncertain Inputs

[ekinugurel]

Are there any manuscripts/write-ups that describe the exact mathematical framework shown in the notebooks for exact GPs with uncertain inputs (i.e., the GaussianSymmetrizedKLKernel) or using SVI?

I've read through a handful of papers from Girard et al., Damianou et al., McHutchon, and Lalchand et al. Though useful, none seem to describe the methods shown in these notebooks. Would appreciate any leads.