> restart;
> ode := `assuming`([(diff(r^2*(diff(`ϕ`(r), r)), r))/r^2 = k[0]^2*`ϕ`(r)+Q*Dirac(r)/`ε`[0]], [Q::positive, (`ε`[0])::positive, (k[0])::positive, r::real]);
> ics := `ϕ`(infinity) = 0, `ϕ`(-infinity) = 0;
> dsolve({ics, ode}, `ϕ`(r), method = fourier);
>