@ARTICLE{Das_j1991_b, author = {J{\"u}rgen~Dassow}, title = {On the connectedness of chain code picture languages}, journal = tcs, year = 1991, volume = 81, number = 2, pages = {289--294}, url = {http://dx.doi.org/10.1016/0304-3975(91)90196-9} }