Finding a Green function for the Helmholtz-like operator with exponential source

[montser]

electromagnetic help!

I have a general question on finding the suitable green function for a given potential for example:
Find the suitable green function for $\nabla^2 \varphi= \frac{1}{l^2} \exp (\frac{-|x|}{l})$

 

[Meir Achuz]

I didn't get to see your Qus.pdf, but if the only BC is \phi-->0 as
r-->infinity, then G=-1/{4\pi|r-r'|}.