list sort( s, j )
	list s;
	int j;
	
	{
	int i;
	list head[M], t;
	struct rec aux;
	extern list Last;
	if (s==NULL)	return(s);
	if ( s->next == NULL )	{Last = s;	return(s);}
	if ( j>D )	{
		for (Last=s; Last->next!=NULL; Last = Last->next);
		return( s );
		}
	for (i=0; i<M; i++)	head[i] = NULL;
	/* Place records in buckets */
	while (s != NULL)	{
		i = charac( j, s->k );
		t = s;
		s = s->next;
		t->next = head[i];
		head[i] = t;
		}
	/* sort recursively */
	t = &aux;
	for (i=0; i<M; i++)	if (head[i]!=NULL)	{
		t->next = sort( head[i], j+1 );
		t = Last;
		}
	return(aux.next);
	}