Invited Papers.- Quantitative vs. Weighted Automata.- Theorem Proving Using Clausal Resolution: From Past to Present.- Population Protocols: Beyond Runtime Analysis.- Recent Advances on Reachability Problems for Valence Systems (Invited Talk).- Regular Papers.- Improvements in Unfolding of Colored Petri Nets.- Reachability of weakly nonlinear systems using Carleman linearization.- Continued Fraction approach to Gauss-Reduction theory.- Absent Subsequences in Words.- Minimal Number of Calls in Propositional Protocols.- Reachability Is NP-Complete Even for the Simplest Neural Networks.-