about pointer to funtion

[Hypatia]

This is a question from Stroustrup's book(The C++ programming language special ed.)

Q: what does the following mean? what would it be good for?
typedef int (&vifii) (int, int);

THE END OF THE Q.

My guess: does this typedef define a type of pointer to function?
but usually it is in the following form:

typedef int (*vifii) (int, int);

Why in the question is there a & instead of *? What's the answer for Stroustup's question?

Thanks in advance.

[Kavin9]

& means reference

int F1(int a, int b){ ... }; 
typedef int (&vifii) (int, int);

int main() 
{ 
int a = 1, b = 3; 
vifii x = F1; 
x(a, b); 
} 

[Hypatia]

so, that means it defines a type of reference to a function? It seems I didnot know this conception from anywhere? As far as I know there is just pointer to function.
Anyway, can you reply the second part of the question? viz. what would it be good for?

[bnbertha]

The same rules apply as the difference between a reference to a variable and a pointer to a variable.