@article{Das_j2005_a, author = {J{\"u}rgen~Dassow and Markus~Holzer}, title = {Language families defined by a ciliate bio-operation: hierarchies and decision problems}, journal = ijfcs, volume = {16}, number = {4}, year = 2005, pages = {645--662}, url = {http://dx.doi.org/10.1142/S0129054105003212} }