Philippe Balbiani, Stanislav Kikot. Sahlqvist Theorems for Precontact Logics. In Thomas Bolander, Torben Braüner, Silvio Ghilardi, Lawrence S. Moss, editors, Advances in Modal Logic 9, papers from the ninth conference on "Advances in Modal Logic," held in Copenhagen, Denmark, 22-25 August 2012. pages 55-70, College Publications, 2012. [doi]