[f2py] external function to subroutines

I'm utterly confused ... As I mentioned in previous posts I want to use 
several external
functions in subroutines. I.e. something like the attached code. What 
I'm I doing wrong.
I.e. can f2py handle this. I'm sorry if I'm nagging you and this turns 
out to be trivial
but I'm completely stuck.

Error is:

sign2map: Confused: external df0t3 is not in lcb_map['f0t3'].
append_needs: unknown need 'df0t3'
append_needs: unknown need 'df0t3'

CODE
_______________

subroutine gap1pl(r, k, b, t, phi3, m, res)
implicit none

integer, parameter :: DP = kind(1.0d0)

!f2py intent (callback) f0t3
!f2py external f0t3
real (DP), external:: f0t3

!f2py intent (callback) df0t3
!f2py external df0t3
real (DP), external:: df0t3

real (DP) :: r, k, b, t, phi3, m, res
real (DP) :: rn2,bamp,meas,tmp,tmpgb,ff0t3
integer :: alpha

intent (in) :: r, k, b, t, phi3, m
intent (out) :: res

!f2py intent (in) r, k, b, t, phi3, m
!f2py intent (out) res

meas=((4.0d0*pi)/(2.0d0*pi)**3)*(r**2)

tmp=0

DO alpha = -1,1,1
     rn2 = r**2 + ((2.0d0*k+1.0d0)*pi*t + alpha*phi3)**2
     ff0t3 = f0t3(rn2)
     bamp = m+b*ff0t3
     tmpgb = -4.d0*t*meas*alpha*((2.0d0*k+1.0d0)*pi*t + &
& alpha*phi3)*((1.0d0+2.0d0*b*bamp*df0t3(rn2))/(rn2+bamp**2)-1/(rn2+m**2))
     tmp = tmp+tmpgb
ENDDO

res=tmp

end subroutine gap1pl