I see a lot of similarities with my dissertation  or .
- the morphisms in  are a restriction of place-preserving morphisms (definition 4.19 and definition 5.27, respectively in ).
- the concept of true morphisms , does not occur, however, the morphisms from an unfolding to the original net system (universal arrows) in  are true.
- Proposition 4 and 5 in  correspond to Lemma 7.40 in ,
- Proposition 6 in  is used/proved in the proof of 7.41
- The unfolding in Theorem 1  is the same as the unfolding in Proposition 7.41  (as mentioned, the universal arrow is true)
-  CPW11 Jean-Michel Couvreur, Denis Poitrenaud, Pascal Weil. Branching Processes of General Petri Nets. in Application and Theory of Petri Nets 2011. LNCS.
-  Walter Keller. Clustering for Petri Nets. Theoretical Computer Science 308 (2003) 145-197.
-  Walter Keller. Petri nets for reverse engineering. Ph. D Thesis, University of Zurich. Available at http://www.ifi.uzh.ch/research/theses-archive/doctoral-theses.html or http://www.wlkl.ch