Invited Papers -- Recognizable Sets of Graphs, Hypergraphs and Relational Structures: A Survey -- Some New Directions and Questions in Parameterized Complexity -- Basic Notions of Reaction Systems -- A Kleene Theorem for a Class of Communicating Automata with Effective Algorithms -- Algebraic and Topological Models for DNA Recombinant Processes -- Contributed Papers -- Regular Expressions for Two-Dimensional Languages Over One-Letter Alphabet -- On Competence in CD Grammar Systems -- The Dot-Depth and the Polynomial Hierarchy Correspond on the Delta Levels -- Input Reversals and Iterated Pushdown Automata: A New Characterization of Khabbaz Geometric Hierarchy of Languages -- On the Maximum Coefficients of Rational Formal Series in Commuting Variables -- On Codes Defined by Bio-operations -- Avoidable Sets and Well Quasi-Orders -- A Ciliate Bio-operation and Language Families -- Semantic Shuffle on and Deletion Along Trajectories -- Sturmian Graphs and a Conjecture of Moser -- P Systems Working in the Sequential Mode on Arrays and Strings -- Optimal Time and Communication Solutions of Firing Squad Synchronization Problems on Square Arrays, Toruses and Rings -- The Power of Maximal Parallelism in P Systems -- An Efficient Pattern Matching Algorithm on a Subclass of Context Free Grammars -- On the Complexity of 2-Monotone Restarting Automata -- On Left-Monotone Deterministic Restarting Automata -- On the Computation Power of Finite Automata in Two-Dimensional Environments -- The Role of the Complementarity Relation in Watson-Crick Automata and Sticker Systems -- The Boolean Closure of Linear Context-Free Languages -- Context-Sensitive Decision Problems in Groups -- Decidability and Complexity in Automatic Monoids -- Relating Tree Series Transducers and Weighted Tree Automata -- An NP-Complete Fragment of LTL -- From Post Systems to the Reachability Problems for Matrix Semigroups and Multicounter Automata -- Words Avoiding -Powers and the Thue–Morse Morphism -- On the Equivalence Problem for E-Pattern Languages Over Small Alphabets -- Complementation of Rational Sets on Countable Scattered Linear Orderings -- On the Hausdorff Measure of ?-Power Languages -- A Method for Deciding the Finiteness of Deterministic Tabled Picture Languages -- Tissue P Systems with Minimal Symport/Antiport.