k-net; parallelogram “letter” condition; admissible relation and admissible algebra
After describing a (general and special) coordinatization of $k$-nets there are found algebraic equivalents for the validity of certain quadrangle configuration conditions in $k$-nets with small degree $k$.
 Belousov, V. D.: Algebraic nets and quasigroups. Kishinev, 1971, in Russian.
 Havel, V.: General nets and their associated groupoids
. Proc.Symp. “n-ary Structures” (1982), Skopje, 229-241. MR 0735655
| Zbl 0583.20057
 Havel, V.: Homomorphisms of nets of fixed degree with singular points on the same line
. Czech. Math. Journ. 26 (1976), 43-54. MR 0392619
| Zbl 0331.50014