C langauge question

int
add(a, b)
  int a;
  int b;
{
}

Rookie question. What's the benefits of this type of declaration? Also, are there any books that teach this indent style? The GNU C Library seems to make use of it. And so does Julian Assange:
http://ftp.cerias.purdue.edu/pub/tools/unix/scanners/strobe/strobe/strobe.c

int
add
        (
    a, b
   )
int a,
   int b;
              {
 return a + b;
}