“…To conclude the introduction, we remind the reader of numerous recent works concerning global existence and decay for coupled wave-Klein-Gordon equations in 1 + 3 dimensions. These include wave-Klein-Gordon equations derived from mathematical physics, such as the Dirac-Klein-Gordon model, the Dirac-Proca and U (1)-electroweak model [14,21,39,40], the Einstein-Klein-Gordon equations [20,25,27,41], the Klein-Gordon-Zakharov equations [15,33,38], the Maxwell-Klein-Gordon equations [24] and certain geometric problems derived from wave maps [1].…”