******** fig4.18 **********

	tree_ptr
	find( element_type x, SEARCH_TREE T )
	{
		if( T == NULL )
			return NULL;
		if( x < T->element )
			return( find( x, T->left ) );
		else
		if( x > T->element )
			return( find( x, T->right ) );
		else
			return T;
	}