Implementing a Declarative String Query Language with String Restructuring. - Raul Hakli; Matti Nykänen; Hellis Tamm; Esko Ukkonen (PADL, 1999)

Adding String Processing Capabilities to Data Management Systems. - Raul Hakli; Matti Nykänen; Hellis Tamm (SPIRE, 2000)

Design and implementation of a string database query language. - Gösta Grahne; Raul Hakli; Matti Nykänen; Hellis Tamm; Esko Ukkonen (Inf. Syst., 2003)

Bideterministic automata and minimal representations of regular languages. - Hellis Tamm; Esko Ukkonen (Theor. Comput. Sci., 2004)

Size Reduction of Multitape Automata. - Hellis Tamm; Matti Nykänen; Esko Ukkonen (CIAA, 2005)

On size reduction techniques for multitape automata. - Hellis Tamm; Matti Nykänen; Esko Ukkonen (Theor. Comput. Sci., 2006)

On Transition Minimality of Bideterministic Automata. - Hellis Tamm (Int. J. Found. Comput. Sci., 2008)

Some Minimality Results on Biresidual and Biseparable Automata. - Hellis Tamm (LATA, 2010)

Minimal DFA for Symmetric Difference NFA. - Brink van der Merwe; Hellis Tamm; Lynette van Zijl (DCFS, 2012)

Quotient Complexities of Atoms of Regular Languages. - Janusz A. Brzozowski; Hellis Tamm (Developments in Language Theory, 2012)

Minimal Nondeterministic Finite Automata and Atoms of Regular Languages - Janusz A. Brzozowski; Hellis Tamm (CoRR, 2013)

Complexity of atoms of Regular Languages. - Janusz A. Brzozowski; Hellis Tamm (Int. J. Found. Comput. Sci., 2013)

Theory of átomata. - Janusz A. Brzozowski; Hellis Tamm (Theor. Comput. Sci., 2014)

Generalization of the Double-Reversal Method of Finding a Canonical Residual Finite State Automaton. - Hellis Tamm (DCFS, 2015)

New Interpretation and Generalization of the Kameda-Weiner Method. - Hellis Tamm (ICALP, 2016)

Lower Bound Methods for the Size of Nondeterministic Finite Automata Revisited. - Hellis Tamm; Brink van der Merwe (LATA, 2017)

Theoretical Aspects of Symbolic Automata. - Hellis Tamm; Margus Veanes (SOFSEM, 2018)

Boolean Automata and Atoms of Regular Languages. - Hellis Tamm (MFCS, 2021)

Quotients and atoms of reversible languages. - Hellis Tamm (Theor. Comput. Sci., 2022)

Duality of lattices associated to left and right quotients. - Jason P. Bell; Daniel Smertnig; Hellis Tamm (AFL, 2023)

Yet another canonical nondeterministic automaton. - Hendrik Maarand; Hellis Tamm (Theor. Comput. Sci., 2024)