Skolem’s problem–on the border between decidability and undecidability V Halava, T Harju, M Hirvensalo, J Karhumäki Technical Report 683, Turku Centre for Computer Science, 2005 | 113 | 2005 |

Positivity of second order linear recurrent sequences V Halava, T Harju, M Hirvensalo Discrete Applied Mathematics 154 (3), 447-451, 2006 | 58 | 2006 |

Undecidability bounds for integer matrices using Claus instances V Halava, T Harju, M Hirvensalo International Journal of Foundations of Computer Science 18 (05), 931-948, 2007 | 56 | 2007 |

Binary (generalized) Post correspondence problem V Halava, T Harju, M Hirvensalo Theoretical computer science 276 (1-2), 183-204, 2002 | 49 | 2002 |

Mortality in matrix semigroups V Halava, T Harju The American Mathematical Monthly 108 (7), 649-653, 2001 | 45 | 2001 |

Undecidability in integer weighted finite automata V Halava, T Harju Fundamenta Informaticae 38 (1-2), 189-200, 1999 | 32 | 1999 |

Decidable and undecidable problems in matrix theory V Halava Turku Centre for Computer Science, 1997 | 32 | 1997 |

Periods and binary words V Halava, T Harju, L Ilie Journal of Combinatorial Theory Series A 89 (2), 298-303, 2000 | 30 | 2000 |

Overlap-freeness in infinite partial words V Halava, T Harju, T Kärki, P Séébold Theoretical Computer Science 410 (8-10), 943-948, 2009 | 29 | 2009 |

Matrix equations and Hilbert's tenth problem P Bell, V Halava, T Harju, J Karhumäki, I Potapov International Journal of Algebra and Computation 18 (08), 1231-1241, 2008 | 27 | 2008 |

Square-free partial words V Halava, T Harju, T Kärki Information Processing Letters 108 (5), 290-292, 2008 | 24 | 2008 |

Undecidability of infinite post correspondence problem for instances of size 9 V Halava, T Harju RAIRO-Theoretical Informatics and Applications-Informatique Théorique et …, 2006 | 23 | 2006 |

Marked PCP is decidable V Halava, M Hirvensalo, R de Wolf Theoretical Computer Science 255 (1-2), 193-204, 2001 | 22 | 2001 |

Relational codes of words V Halava, T Harju, T Kärki Theoretical computer science 389 (1-2), 237-249, 2007 | 21 | 2007 |

Tighter undecidability bounds for matrix mortality, zero-in-the-corner problems, and more J Cassaigne, V Halava, T Harju, F Nicolas arXiv preprint arXiv:1404.0644, 2014 | 16 | 2014 |

Decidability of the binary infinite Post Correspondence Problem V Halava, T Harju, J Karhumäki Discrete applied mathematics 130 (3), 521-526, 2003 | 16 | 2003 |

Generalized Post correspondence problem for marked morphisms V Halava, T Harju, M Hirvensalo International Journal of Algebra and Computation 10 (06), 757-772, 2000 | 16 | 2000 |

Interaction properties of relational periods V Halava, T Harju, T Kärki Discrete Mathematics & Theoretical Computer Science 10, 2008 | 15 | 2008 |

On the number of squares in partial words V Halava, T Harju, T Kärki RAIRO-Theoretical Informatics and Applications 44 (1), 125-138, 2010 | 14 | 2010 |

On Markov's undecidability theorem for integer matrices V Halava, T Harju Semigroup Forum 75, 173-180, 2007 | 14 | 2007 |