g++ troubles with templates

Hello,
I have trouble with g++ code related to templates in program of
mine,

perhaps anybody can help me with that.
I might am doing something wrong with the template names....

Compiling my code, I get the compiler error:
(Yes, I broke the compiler outputs in order to make it more readable)

What is wrong?
                Willy

-----------------------------
g++ -g -I. -D___x86___ -D_DEBUG -Wall MainAsx.o PCMFile.o asxio.o
\ FhxError.o Unix4Win.o perrorf.o \
         ftt_recursive.o ftt_heterogen.o ftt_base.o pointfield.o pointfield_deconvolute.o pointfield_convolute.o -
o asx -lm

MainAsx.o: In function `CalcHFtt2Asx(unsigned int, unsigned int,
double, char*, char*, bool)':
/home/duffy/hafi/Documents/prj/SCIENTIA/PHYSIK/ASX/asx/sw/MainAsx.cpp:
48:
undefined reference to
`FttRecursive<std::complex<double>>::FttRecursive(unsigned int,
unsigned int, double, double)'
collect2: ld returned 1 exit status
make: *** [asx] Fehler 1

------------------------------
------------------------------ I initiate the FttRecursive herein:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <math.h>
#include <complex>

#include "Unix4Win.h"
#include "ftt.h" //this includes both ftt_base.h and ftt_recursive.h

long FrameCount=0;

int CalcHFtt2Asx(unsigned int N,
                 unsigned int R,
                double a ,
                char *input,
                char *output,
         bool recursive)
{
        /* .... */
        t_ptr_FttBase ftt;
        if(recursive) ftt=new FTT(N,R,a,Tx);
        else /*...*/
        /*...*/
}
===========================

----------------------------- in file ftt_recursive.h I declare:

#ifndef __FTT_RECURSIVE_H
#define __FTT_RECURSIVE_H

#include <complex>
#include <math.h>

#include "ftt_base.h"
template<class t_Data >
class FttRecursive
        : public FttBase<t_Data >
{
public:
                FttRecursive(unsigned int N=32, unsigned int R=32,
double a=0.010, double Tx=1.0/11025 );
        virtual ~FttRecursive() {};

        virtual t_Data *const calc(double *pcm);

protected:
        const double E;
};

typedef FttRecursive<std::complex<double> > FTT;

#endif
===========================
------------------------------ in file ftt_recursive.cpp i define:
#include <math.h>
#include <complex>

#include "ftt_recursive.h"

template<class t_Data >
FttRecursive<t_Data >::FttRecursive(unsigned int N_, unsigned int R_,
double a_, double Tx_)
        : FttBase<t_Data>( N_, R_, a_, Tx_)
        , E(exp(-a_*Tx_))
{

}

===========================
----------------------------- in file ftt_base.h I declare:
#ifndef __FTT_BASE_H
#define __FTT_BASE_H

#include <complex>
#include <math.h>

#include "pointfield.h"

template<class t_Data>
class FttBase
{
public:
                FttBase(unsigned int N=32, unsigned int R=32, double
a=0.010, double Tx=1.0/11025);
        virtual ~FttBase();

        virtual t_Data *const calc(double *pcm)=0;

        t_Data* const convolute(t_Data* con_in_spectrum);

protected:
        const std::complex<double> I;

        unsigned int L;

        unsigned int N,R;

        double a;
        double Tx;

        unsigned int M;
        t_Data *P_M;

        PointField<t_Data> target;
        PointField<t_Data> source;
        PointField<t_Data> psf;

        bool create_psf(PointField<t_Data> &PSF);

        t_Data psf_value_function(double delta_w, double delta_t);
};

typedef FttBase<std::complex<double> > *t_ptr_FttBase;

#endif

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