@ARTICLE{NavaraPtakDifference,
  MYNOTE =   { (written 1992!) S1996, A1996, P1997 },
  AUTHOR =   {Navara, Mirko and Pt{\'a}k, Pavel},
  TITLE =   {Difference posets and orthoalgebras},
  JOURNAL =   {Bull. for Studies and Exchanges on Fuzziness and Its
                  Appl.},
  YEAR =   {1997},
  VOLUME =   {69},
  PAGES =   {64--69},
  importance =   {1},
  psurl =   {[PostScript,
                  k]},
}