principal congruences; poset algebra; commutative groupoid; principal tolerances; partiallz ordered set; tolerance; congruence
To everz partiallz ordered set a certain groupoid is assigned. A tolerance on it is defined similarlz as a congruence, onlz the requirement of transitivitz is omitted. Some theorems concerning these tolerances are proved.
 Pöschel R.: Graph vaгieties. Preprint, Institut der Mathematik, Akad. Wiss. DDR, Berlin, 1985.