[Ba] Bartol W.:
Weak subalgebra lattices. Comment. Math. Univ. Carolinae 31 (1990), 405-410.
MR 1078473 |
Zbl 0711.08007
[Bur] Burmeister P.:
A Model Theoretic Oriented Approach to Partial Algebras. Mathematical Research Band 32, Akademie Verlag, Berlin, 1986.
MR 0854861 |
Zbl 0598.08004
[Ore] Ore O.:
Graphs and correspondences, Festschrift Andreas Speiser. Zürich (1945), 184-191.
MR 0013899