Geodesic
The Entropy of an Automorphism of a Solenoidal Group
Teoriâ veroâtnostej i ee primeneniâ, Tome 4 (1959) no. 3, pp. 249-254 
L. M. Abramov. The Entropy of an Automorphism of a Solenoidal Group. Teoriâ veroâtnostej i ee primeneniâ, Tome 4 (1959) no. 3, pp. 249-254. http://geodesic.mathdoc.fr/item/TVP_1959_4_3_a0/
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     author = {L. M. Abramov},
     title = {The {Entropy} of an {Automorphism} of a {Solenoidal} {Group}},
     journal = {Teori\^a vero\^atnostej i ee primeneni\^a},
     pages = {249--254},
     year = {1959},
     volume = {4},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TVP_1959_4_3_a0/}
}
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Voir la notice de l'article provenant de la source Math-Net.Ru

Let us denote by $X$ a group of characters for the subgroup $R$ of an additive group of rational numbers and by $T$ its automorphism adjoint to the automorphism of the group $R$, which is given by multiplying by the irreducible fraction ${m/n}$. In this paper it is proved that the entropy of such an automorphism equals $\log(\max\{|m|,n\})$.