interesting problem( map<int , vector<string > & > tmp; // it donot work )

Hi All ,

i am getting an interesting problem
  map<int , vector<string > & > tmp; // it donot work
  map<int , vector<string > * > tmp; // it work

++++++++++++++++++++++++++++++++++++++++++++++++

kindly let me know the reason

#include <iostream.h>
#include <map>
#include <vector>
#include <string>

using namespace std;

int main()
{
  vector< string > v1 , v2;
  map<int , vector<string > & > tmp;
  map<int , vector<string > & >::iterator iter1,iter2;
  tmp.insert(pair<int ,vector<string> & >(1,v1));
  tmp.insert(pair<int ,vector<string> & >(2,v2));

  v1.push_back("Pallav1");
  v1.push_back("Sharmad1");
  v1.push_back("Ajay1");

  v2.push_back("Pallav2");
  v2.push_back("Sharmad2");
  v2.push_back("Ajay2");

  for(int i = 0 ; i < v1.size() ; i++ )
    cout<< v1.at(i) << endl;

  for(int i = 0 ; i < v2.size() ; i++ )
    cout<< v2.at(i) << endl;

  iter1 = tmp.begin();
  iter2 = tmp.end();

  for(iter1 ; iter1 != iter2 ; iter1++ )
    { cout<<"++++++++++++++++++++++++++++++++++++"<<endl;
      cout<<"first value :: "<<(*iter1).first ;
      for(int i = 0 ; i < ((*iter1).second)->size() ;i++)
        cout<<((*iter1).second)->at(i) <<endl;
   }

   return 0;
}

Thanks
Pallav Singh