no. 1
Decidability and undecidability of theories of abelian groups with predicates for subgroups
Compositio Mathematica, Tome 31 (1975) no. 1, pp. 23-30. 
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     author = {Baur, Walter},
     title = {Decidability and undecidability of theories of abelian groups with predicates for subgroups},
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     pages = {23--30},
     publisher = {Noordhoff International Publishing},
     volume = {31},
     number = {1},
     year = {1975},
     mrnumber = {384525},
     zbl = {0335.02032},
     language = {en},
     url = {http://archive.numdam.org/item/CM_1975__31_1_23_0/}
}
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Baur, Walter. Decidability and undecidability of theories of abelian groups with predicates for subgroups. Compositio Mathematica, Tome 31 (1975) no. 1, pp. 23-30. http://archive.numdam.org/item/CM_1975__31_1_23_0/

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