20K99 3 03E75 2 20F99 2 partition of a group 2 20B10 1 20B30 1 20C99 1 20M10 1 20M18 1 20M30 1 20N99 1 Abelian digroups 1 actions and representations 1 digroups 1 groups 1 k-thin subsets of a group 1 semigroups 1 sparse subset of a group 1 symmetric digroups 1