subroutine ftlagslow( nyq, lag, t0,dt, n1, ctt)
integer nyq, n1, ie
real lag, t0, dt, f0, df, freq
complex ctt(n1), cexp, cmplx
temporary complex cff(n1)

call slowft( 0, 0, nyq, t0, dt, n1, ctt, f0, df, n1, cff)

do ie= 1, n1 {  freq= f0 + (ie-1)*df
	if( ie==1  &  nyq > 0)
		cff(1)  = cff(1)  * cos(            2.*3.14159265 * freq * lag )
	else
		cff(ie) = cff(ie) * cexp( cmplx(0., 2.*3.14159265 * freq * lag))
	}
call slowft( 1, 0, nyq, t0, dt, n1, ctt, f0, df, n1, cff)
	
return; end