Chadlia Jerad and  Amel Grissa-Touzi and  Habib Ounelli,  STRPRO Tool for Manipulation of Stratified Programs Based on SEPN.   journal   = {International Journal of Computer, Electrical, Automation, Control and Information Engineering}, [online]. World Academy of Science, Engineering and Technology. November 2007, vol. 11(11). 3578 - 3581[viewed 18 February 2019]. Available from: http://waset.org/publications/6905.