i am trying to find resources on the derivation of the fundamental solution to the radial wave equation. any suggestions of or links to books, papers, and/or notes would be much appreciated. i have tried searching google, arxiv, etc. for information, but i haven't come up with anything useful yet. there's a lot of material pertaining to physics concerning using the solution, but i need the derivation.

i've been learning about solutions to the wave equation for euclidean dimensions 1-3 (d'Alembert's formula, spherical means, method of descent), and the above is my next task. if you have any general insight about the radial wave equation, this would be helpful as well. thanks!

(background: 3rd year graduate student in mathematics)

**edit**: if no one has any specific references to the derivation, then what about context? does the spherically symmetric wave equation mean the same thing as the radial wave equation? i know that seems like a possibly ignorant question, but to someone unfamiliar with or new to this, i think it's good to be cautious and not say well they sound the same.