@article {401, title = {On acceptance conditions for membrane systems: characterisations of L and NL}, journal = {The Complexity of Simple Programs}, year = {2008}, month = {December}, pages = {225-242}, publisher = {Cork University Press}, address = {Cork, Ireland}, isbn = {978-1-906642-00-6}, url = {http://www.cs.us.es/~dwoods/download/MurphyWoods-CSP08.pdf}, author = {Niall Murphy and Damien Woods}, editor = {Turlough Neary and Damien Woods and Anthony K. Seda and Niall Murphy} }