@article {2354, title = {An apparently innocent problem in Membrane Computing}, journal = {Seventeenth Brainstorming Week on Membrane Computing,}, year = {2019}, pages = {127-138}, url = {http://www.cs.us.es/~marper/investigacion/apparently-innocent.pdf}, author = {David Orellana-Mart{\'\i}n and Luis Valencia-Cabrera and Agust{\'\i}n Riscos-N{\'u}{\~n}ez and Mario J. P{\'e}rez-Jim{\'e}nez} }