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Let $G$ be a group and $m$ be an integer greater than or equal to $2$. $G$ is said to be $m$-permutable if every product of $m$ elements can be reordered at least in one way. We prove that, if $G$ has a centre of finite index $z$, then $G$ is $(1+[z/2])$-permutable. More bounds are given on the least $m$ such that $G$ is $m$-permutable.

Let G be a supersolvable finite group or a solvable one, in which the orders of principal factors are primes or squares of primes; and let exp G divide $n=p_1^{a_1}{p}_2^{a_2}\mathrm{\cdots }{p}_s^{a_s}$ ($p_1>p_2>\mathrm{\cdots }>p_s$ prime numbers). A much simple enunciation is given for essentially known theorems on some systems of laws characterizing G; it is indeed shown that the laws 1.(1) and 1.(2) can be removed from the enunciates of such theorems, getting equivalent systems of laws characterizing G.

Let $G$ be a group and $m$ be an integer greater than or equal to $2$. $G$ is said to be $m$-permutable if every product of $m$ elements can be reordered at least in one way. We prove that, if $G$ has a centre of finite index $z$, then $G$ is $(1+[z/2])$-permutable. More bounds are given on the least $m$ such that $G$ is $m$-permutable.