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and
denote the varieties of groups defined by the laws (xy)
(n)-groups were termed “n-abelian” by R. Baer [1] and have been a subject matter of investigation by various authors (see [3], [5], [6] and the references therein). Recently KaluŽnin [5] has shown that
, thus clarifying the relationship between U(n) and the familiar varieties. From the elementary inequalities

but
for any
Thus
and
. It is also easy to see that in general
(see for instance [6] § 5.1) and we are led to ask