ELECTRONIC	h   t   t   p   c o l o n   s l a s h   s l a s h   w   w   w dot m a t h e m a t i k dot t u   d a s h   b   s dot d   e   s l a s h   h a r b o r t h   s l a s h	http://www.mathematik.tu-bs.de/harborth/	1