Basic facts about all groups that can be obtained directly from the group axioms are commonly subsumed under elementary group theory. For example, repeated applications of the associativity axiom show that the unambiguity of a ⋅ ⋅ b ⋅ ⋅ c = ( a ⋅ ⋅ b ) ⋅ ⋅ c = a ⋅ ⋅ ( b ⋅ ⋅ c ) generalizes to more than three factors. Because this implies that parentheses can be inserted anywhere within such a series of terms, parentheses are usually omitted.