Linker error when dividing source code into multiple files

Hi all;

I have written a class, and it works fine when all the definitions are
in one main.cpp file. But whenever I divide source code in several
files(main.cpp, class.h, class.cpp), it is compiled with no errors,
but linker gives the following error. I could not find what the
problem is.

Thanks

yatko
----
**** Build of configuration Debug for project test ****

make all
Building target: test
Invoking: GCC C++ Linker
g++ -o"test" ./ProducersNConsumers.o ./main.o -lboost_thread-gcc41-
mt-1_34_1
../main.o: In function `main':
/home/oktay/workspace/test/Debug/../main.cpp:135: undefined reference
to `ProducersNConsumers<int>::ProducersNConsumers()'
/home/oktay/workspace/test/Debug/../main.cpp:151: undefined reference
to `ProducersNConsumers<int>::~ProducersNConsumers()'
collect2: ld returned 1 exit status
make: *** [test] Error 1
-----

main.cpp
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
#include <boost/thread/thread.hpp>
#include <iostream>

#include "ProducersNConsumers.h"

boost::mutex io_mutex;
const int BUFFER_SIZE = 1024;
const int ITERS = 100;

volatile bool start = false;

int
main()
{
    ProducersNConsumers<int> outgoing;

    return 0;
}
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ProducersNConsumers.h
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
#ifndef PRODUCERSNCONSUMERS_H_
#define PRODUCERSNCONSUMERS_H_

#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <list>

extern boost::mutex io_mutex;
extern const int BUFFER_SIZE;
extern const int ITERS;

template <class DataType>
class ProducersNConsumers
{

public:

    typedef boost::mutex::scoped_lock scoped_lock;

    ProducersNConsumers();

    ~ProducersNConsumers();

    DataType Pop(void);

    void Push(DataType);

    void Print(void);

private:

    struct Node {
        DataType data;
        bool valid;

        Node(DataType, bool);
    };

    int itemCount;

    std::list<Node> buffer;

    typename std::list <Node>::iterator popIterator;
    typename std::list <Node>::iterator pushIterator;

    boost::mutex enter;
    boost::condition full;
    boost::condition empty;

};

#endif /*PRODUCERSNCONSUMERS_H_*/
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ProducersNConsumers.cpp
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
#include <iostream>

#include "ProducersNConsumers.h"

template <class DataType>
ProducersNConsumers<DataType>::Node::Node(DataType data = 0, bool
valid = false)
{
    }

template <class DataType>
ProducersNConsumers<DataType>::ProducersNConsumers()
{
    }

template <class DataType>
ProducersNConsumers<DataType>::~ProducersNConsumers()
{

}

template <class DataType>
DataType
ProducersNConsumers<DataType>::Pop(void)
{

}

template <class DataType>
void
ProducersNConsumers<DataType>::Push(DataType data)
{

}

template<class DataType>
void
ProducersNConsumers<DataType>::Print(void)
{
    scoped_lock lock(enter);

}
--------------------------------------------------------------------------------------------------------------------------------------------------------------------