C++ singleton Pattern _ Implementation and memory managenet

my code below is not comiling for the singleton pattern

(error LNK2019: unresolved external symbol "private: __thiscall Singleton::Singleton(void)" (??0Singleton@@AAE@XZ) referenced in function "public: static class Singleton * __cdecl Singleton::returnOneInstance(void)" (?returnOneInstance@Singleton@@SAPAV1@XZ))

can anyone help? i also want to know how one must manage the memory? thanks

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <iterator>

using namespace std;

class Singleton
{
private:
    Singleton();
    Singleton(const Singleton& sing);
    void operator=(const Singleton& sing);
    static Singleton* singleton;
    /*The 'instance' field holds the reference of the one and only instance.
      It is stored in a static variable because its scope has to be the class itself and not a particular instance.
    */
public:
    static Singleton* returnOneInstance();
    void printme() const;
};

Singleton* Singleton::singleton=NULL;
Singleton* Singleton::returnOneInstance(){
    if (!singleton){
        singleton=new Singleton;
    }
    return singleton;
};

void Singleton::printme()const {
    cout << "I'm the Singleton" << endl;
}

int main()

{
    Singleton* m=Singleton::returnOneInstance();
    m->printme();

    system("PAUSE");
    return 0;
}