Motivated by Gumm's Shifting lemma and Shifting principle the present paper relates analogous triangular and trapezoid lemmas and principles to the distributivity of congruence lattices of single algebras and varietes.
Motivated by Gumm's Shifting lemma and Shifting principle the present paper relates analogous triangular and trapezoid lemmas and principles to the distributivity of congruence lattices of single algebras and varietes. (en)