C++ Basic concept regarding reference operator return type

I need to clear a basic concept. This code works fine. Can somebody explain me that if the function calDouble already returning the address (reference) of int why I need to use & operator further in main int *j = &calDouble(i); to get the address (reference) of int? Thanks.

int& calDouble(int x)
{
    x = x*2;
    return x;

}

int main(int argc, char *argv[])
{
    int i = 99;
    int *j = &calDouble(i);

    system("PAUSE");
    return EXIT_SUCCESS;
}