@InProceedings{FerSti_j2002_b, author = {Henning~Fernau and Ralf~Stiebe}, title = {Valuated and Valence Grammars: an Algebraic View}, booktitle = {Developments in Language Theory, DLT 2001}, pages = {281--292}, year = 2002, editor = {Werner~Kuich}, publisher = springer }