"This monograph presents a significant new result in general relativity. In particular, it provides a proof related to the Einstein-Klein-Gordon equation, a fundamental equation in mathematical physics that couples the Einstein equation of general relativity with a matter field described by the Klein-Gordon equation. The book begins with an introduction and history of the subject, proceeds to prove several auxiliary lemmas, and culminates in the central proof. This book represents a significant advance in mathematical physics, and provides the most cutting-edge treatment of the Einstein-Klein-Gordon equation to date"--