Checking Relativistic Electrodynamics calculations: D'alembertian in Mathematica

How to define the D'alembert Operator, as a function of 4 other functions in 4 variables; the speed of light c is made =1 in this notebook. 
Note how a component of the 4-Vector Potential A, defined in terms of r (=sqrt( x^2 + y^2 ) ), produces a steady value of one component of J, the 4-current vector.

Google Drive folder with downloadable file: https://drive.google.com/folderview?id=0B36YNo_GwIhxb1F4TkVFdEtsY0U&usp=sharing
Filename: Dalembertian.nb