Fig. 5.5 — Vector spherical harmonics
Resonances, waves and fields: Spherical harmonics
Image result for Maxwell–Cartesian spherical harmonics
Image result for geodesy for the layman SPHERICAL HARMONICS
Relations between polar coordinates, spherical harmonics, Cartesian coordinates, anatomy and flight mechanics all seen from the same perspective.
The science of Spherical Harmonics at Weta Digital
Spherical harmonics - Wikipedia, the free encyclopedia