Artiom Alhazov Rudolf Freund Marion Oswald Sergey Verlan Partial Halting in P Systems Using Membrane Rules with Permitting Contexts. 110-121 2007 conf/mcu/2007 MCU http://dx.doi.org/10.1007/978-3-540-74593-8_10 db/conf/mcu/mcu2007.html#AlhazovFOV07