@article {263, title = {Matrix Languages, Register Machines, Vector Addition Systems}, journal = {Third Brainstorming Week on Membrane Computing}, year = {2005}, month = {1/31//05-2/4/05}, pages = {155-167}, publisher = {F{\'e}nix Editora}, address = {Sevilla, Espa{\~n}a}, isbn = {84-609-6771-9}, author = {Rudolf Freund and Oscar Ibarra and Gheorghe Paun and H. C. Yen}, editor = {M. A. Guti{\'e}rrez Naranjo and Agust{\'\i}n Riscos-N{\'u}{\~n}ez and Francisco J. Romero-Campero and Dragos Sburlan} }