;
; SUMMATIONS Phir=dPhi/dr,Phith=dPhi/dth,and Phiph=dPhi/dphi
; Hr & dHr include the effect of various models
;
pro zbrtp,r,sthi,Hr,dHr,Pi,dPi,Gfj,dGfj,Br,Bt,Bp,N0=n0

    if not keyword_set(n0) then n0=1 else n0=0
    nmax=n_elements(Hr)-1
    Phir = 0.
    Phith = 0.
    Phiph = 0.
    for n=n0, nmax do begin
        for m=0, n do begin
            Phir= Phir + dHr(n)*Pi(n,m)*Gfj(n,m)
            Phith= Phith + Hr(n)*dPi(n,m)*Gfj(n,m)
            Phiph= Phiph + Hr(n)*Pi(n,m)*dGfj(n,m)
        endfor
    endfor
    Br = -1.* Phir    
    Bt = -1.* Phith/r
    Bp = -1.* Phiph/r/sthi

end