@article {1912, title = {Minimal cooperation in P systems with symport/antiport: A complexity approach}, journal = {Thirteenth Brainstorming Week on Membrane Computing}, year = {2015}, month = {02/2015}, pages = {301-323}, publisher = {F{\'e}nix Editora}, edition = {1}, address = {Sevilla, Espa{\~n}a}, url = {http://www.cs.us.es/~marper/investigacion/proceedings-13th-BWMC.pdf}, author = {Luis Valencia-Cabrera and Bosheng Song and Luis F. Mac{\'\i}as-Ramos and Linqiang Pan and Agust{\'\i}n Riscos-N{\'u}{\~n}ez and Mario J. P{\'e}rez-Jim{\'e}nez} }