Volume 38, Numbers 1-2, March-April 1999 Special issue dedicated to Arto Salomaa
: On the Circuit Depth of Structurally Reversible Cellular Automata.
: Subwords and Power-Free Words are not Expressible by Word Equations.
: Solving Equivalence of Recurrent Sequences in Groups by Polynomial Manipulation.
: The Equivalence Problem of D0L and DF0L Power Series.
: On the Decidability of Some Problems Concerning Morphisms, Regular Sets, and Post Correspondence Problem.
Volume 38, Number 3, May 1999
: Multi-Bracketed Contextual Rewriting Grammars.
Volume 38, Number 4, June 1999