A. Widom and L. Larson, "Ultra low momentum neutron catalyzed nuclear reactions on metallic hydride surfaces," European Physical Journal C (2006).
This appears to be the first of an important series of paper in the field of cold fusion. It suggests that what is taking place in systems is not fusion, per se, in which two positively charged nuclei overcome Coulomb repulsion to fuse into a new nucleus. Instead what is happening is that inverse beta decay is taking place, where neutrons generated from free electrons and protons. The neutrons then meander about at low energies and are absorbed, one after another, into the nuclei of nearby atoms. As they load, one after another, into these atoms, the atomic mass changes and eventually the atoms decay into other elements. There are different chains of decay, some of which release significant amounts of energy, which manifests itself in part in the form of heat given off by the system.
The paper has main two parts. The first part attempts to provide support for inverse beta decay through an elaboration of ideas found in earlier literature, and the second part illustrates one concrete radioactive decay path. The first part gets into some math I'm unfamiliar with, whereas it is not difficult to imagine applying the ideas set out in the second part to the construction of a basic numerical model that attempts to predict, or at least explain, the ratios of residual isotopes found in some of the experiments.