Course Textbook
Tutorial on Petri Nets (ACM Computing Surveys. Volume 9 , Issue 3 (September 1977). Title: Petri Nets. Author: James L. Peterson
Introduction. Get the Chapter 1 from Prof. Zeigler's website. You can read the introductory materials in the book "Theory of modelling and simulation", by B. Zeigler, H. Praehofer and T. Kim
Information on Cell-DEVS can be found here