A. Haque. Economics, Commerce and Trade Management: An International Journal (ECTIJ), volume 1 of IFIP Advances in Information and Communication Technology, page 15-25. https://airccse.com/ectij/papers/1117ectij02.pdf, (2017)
K. Hoffmann, H. Ehrig, and T. Mossakowski. 26th International Conference On Application and Theory of Petri Nets and Other Models of Concurrency, volume 3536 of Lecture Notes in Computer Science, Springer Verlag, London, (2005)