@InProceedings{martin_et_al:DagSemProc.09441.5,
  author =	{Martin, Barnaby and Martin, Jos},
  title =	{{The complexity of positive first-order logic without equality II: The four-element case}},
  booktitle =	{The Constraint Satisfaction Problem: Complexity and Approximability},
  pages =	{1--12},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2010},
  volume =	{9441},
  editor =	{Andrei A. Bulatov and Martin Grohe and Phokion G. Kolaitis and Andrei Krokhin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.09441.5},
  URN =		{urn:nbn:de:0030-drops-23670},
  doi =		{10.4230/DagSemProc.09441.5},
  annote =	{Keywords: Quantified constraints, Galois connection}
}