@Inproceedings{EPTCS90.3, author = {Salo, Ville and T\"orm\"a, Ilkka}, year = {2012}, title = {On Derivatives and Subpattern Orders of Countable Subshifts}, editor = {Formenti, Enrico}, booktitle = {{\rm Proceedings 18th international workshop on} Cellular Automata and Discrete Complex Systems {\rm and 3rd international symposium} Journ\'ees Automates Cellulaires, {\rm La Marana, Corsica, September 19-21, 2012}}, series = {Electronic Proceedings in Theoretical Computer Science}, volume = {90}, publisher = {Open Publishing Association}, pages = {23-36}, doi = {10.4204/EPTCS.90.3}, }