Cited passages: Richard Fitzpatrick, Pulse Propagation, equation 9.7: the deep-water gravity-capillary dispersion relation; Richard Fitzpatrick, Pulse Propagation, equations 9.9–9.16: first-order expansion and envelope translation; subsequent discussion explains the neglected curvature.
Cited passages: Richard Fitzpatrick, Wave-Front Propagation, 27 June 2014, equations 871–873 and following discussion: no field before t=x/c in the causal dielectric model.