LAUSR

A subset [Formula: see text] of an Abelian group [Formula: see text] is called a difference basis of [Formula: see text] if each element [Formula: see text] can be written as the difference [Formula: see text] of some elements [Formula: see text]. The smallest cardinality [Formula: see text] of a difference basis [Formula: see text] is called the difference size of [Formula: see text] and is denoted by [Formula: see text]. We prove that for every [Formula: see text] the cyclic group [Formula: see text] of order [Formula: see text] has difference size [Formula: see text]. If [Formula: see text] (and [Formula: see text]), then [Formula: see text] (and [Formula: see text]). Also, we calculate the difference sizes of all cyclic groups of cardinality [Formula: see text].