olemus
rühmoid, mille binaartehe on assotsiatiivne

ülevaateid
http://mathworld.wolfram.com/Semigroup.html

http://math.uga.edu/~pete/semigroup.pdf

http://math.arizona.edu/~jaytaylor/files/york/SemigroupTheory.pdf

näiteid
http://planetmath.org/examplesofsemigroups

rakendusi
https://journalofscience.org/index.php/GJSFR/article/download/1541/1402

https://shannoninstitute.ucd.ie/~semiring/diss_oliver.pdf