subroutine ftderivslow( nyq, t0,dt, ntf, ctt, cdd)
integer nyq, ntf, ie
real t0,dt,f0,df, freq
complex ctt(ntf), cdd(ntf), cmplx
temporary complex cff(ntf)
call slowft( 0, 0, nyq, t0, dt, ntf, ctt, f0, df, ntf, cff)

do ie= 1, ntf {  freq= f0+(ie-1)*df
	cff(ie) = cff(ie) *  cmplx( 0., - 2. * 3.141549265 * freq )
	}
if( nyq > 0 )						#  if( omega0 == -pi/dt)
	cff(1) = 0.

call slowft( 1, 0, nyq, t0, dt, ntf, cdd, f0, df, ntf, cff)
return; end