@InProceedings{bell_et_al:LIPIcs.MFCS.2019.70,
  author =	{Bell, Paul C. and Hirvensalo, Mika},
  title =	{{Acceptance Ambiguity for Quantum Automata}},
  booktitle =	{44th International Symposium on Mathematical Foundations of Computer Science (MFCS 2019)},
  pages =	{70:1--70:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-117-7},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{138},
  editor =	{Rossmanith, Peter and Heggernes, Pinar and Katoen, Joost-Pieter},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2019.70},
  URN =		{urn:nbn:de:0030-drops-110149},
  doi =		{10.4230/LIPIcs.MFCS.2019.70},
  annote =	{Keywords: Quantum finite automata, matrix freeness, undecidability, Post’s correspondence problem, quaternions}
}