;
; SUMMATIONS Phir=dPhi/dr,Phith=dPhi/dth,and Phiph=dPhi/dphi
; NOTE: Hr & dHr here include the effect of various models
;
pro brtp,Nmax,apar,r,sthj,Hr,dHr,Pj,dPj,Gfi,dGfi,Br,Bt,Bp,N0=n0

    if keyword_set(n0) then n1=0 else n1=1
    Phir = double(0.0)
    Phith = double(0.0)
    Phiph = double(0.0)
    for n=n1, Nmax do begin
        for m=0, n do begin
            Phir= Phir + dHr(n)*Pj(n,m)*Gfi(n,m)
            Phith= Phith + Hr(n)*dPj(n,m)*Gfi(n,m)
            Phiph= Phiph + Hr(n)*Pj(n,m)*dGfi(n,m)
        endfor
    endfor
    Br = -1.* Phir    
    Bt = -1.* Phith/r
    Bp = -1.* Phiph/r/sthj

end