Geodesic
On Differential Rational Invariants of Finite Subgroups of Affine Group
Bulletin of the Malaysian Mathematical Society, Tome 28 (2005) no. 1 
Bekbaev Ural. On Differential Rational Invariants  of Finite Subgroups
  of Affine  Group. Bulletin of the Malaysian Mathematical Society, Tome 28 (2005) no. 1. http://geodesic.mathdoc.fr/item/BMMS_2005_28_1_a5/
@article{BMMS_2005_28_1_a5,
     author = {Bekbaev Ural},
     title = {On {Differential} {Rational} {Invariants}  of {Finite} {Subgroups
}  of {Affine}  {Group}},
     journal = {Bulletin of the Malaysian Mathematical Society},
     year = {2005},
     volume = {28},
     number = {1},
     url = {http://geodesic.mathdoc.fr/item/BMMS_2005_28_1_a5/}
}
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  of Affine  Group
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Voir la notice de l'article provenant de la source BMMS

In the case of differential field an algebraic analogue of the field of all invariant differential rational functions of surfaces relative to gauge transformations and different subgroups of affine motion group is introduced. In the case of finite subgroup of affine group it is proved that its field of invariant rational functions generates the above field of invariant differential rational functions as a some differential field.