reserve  X for non empty set,
  R for Relation of X;
reserve O for non empty RelStr;
reserve O for non empty OrthoRelStr;
reserve QO for QuasiOrdered non empty OrthoRelStr;

theorem
  for PO being non empty OrthoRelStr, f being UnOp of the carrier of PO
  st f OrthoComplement_on PO holds f QuasiOrthoComplement_on PO;
