The author of the Short Note, “Straightforward Derivation of Hubral's Wavefront Curvature Differential Equation in Inhomogeneous Isotropic Media,” Th. Krey, has forwarded the following changes to his paper which appeared in May Geophysics, p. 964–967.
In equations (19) and (20), C0 should be replaced by (C0/v0); and in equation (21), C is replaced by (C/v).
In equation (10) the product A0·r1T is replaced by r1·A0.
The last sentence ahead of the “acknowledgement” paragraph should be replaced by the following:
The third term appears only if the velocity is a nonlinear function of x, y, z.