The Citation Funnel is a research framework for machine attribution. A machine citation is not a direct link between a claim and a source; it is the visible output of a five-stage process. A source must be reachable, salient, supportive, relied upon, and favored by deployment priors before it is ever cited. This book names the divergence between sources that support a claim and sources that receive credit the Support-Citation Gap, synthesizes fifteen research literatures into one vocabulary, states six falsifiable propositions, and sets out a complete, reproducible study protocol. Published by ZAIQ.