Ordered groupoids and étendues
Ordered semigroups containing minimal and maximal elements.
Ordered sets which support inverse semigroups : Three examples.
Ordering D-classes and computing Schein rank is hard.
Ordering the local subsemigroups of a semigroup.
Ordering the symmetric group: why using the Iwahori-Hecke algebra? (Ordonner le groupe symétrique: Pourquoi utiliser l'algèbre de Iwahori-Hecke?)
Orders of some modular linear groups.
Orders of subsemigroups of Tn.
Ordre maximal d’un élément du groupe des permutations et «highly composite numbers»
Ordre minimum des boucles de Moufang commutatives de classe 2 (Resp. 3)
Ordres maximaux
Orthodox bands of modules
Orthodox congruences on regular semigroups.
Orthodox semidirect products and wreath products of monoids.
Orthodox semigroups.
Orthodox semigroups whose idempotents satisfy a certain identity.
Orthodox semigroups with complemented congruence lattices.
Orthodox -semigroups.
Orthogonal Groups of Dyadic Unimodular Quadratic Forms.
Orthogonal representations of Galois groups, Stiefel-Whitney classes and Hasse-Witt invariants.