no. 2
Perfect systems
Compositio Mathematica, Tome 19 (1968) no. 2, pp. 95-166. 
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     author = {Mahler, K.},
     title = {Perfect systems},
     journal = {Compositio Mathematica},
     pages = {95--166},
     publisher = {P. Noordhoff N. V., Groningen},
     volume = {19},
     number = {2},
     year = {1968},
     mrnumber = {239099},
     zbl = {0168.31303},
     language = {en},
     url = {http://www.numdam.org/item/CM_1968__19_2_95_0/}
}
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Mahler, K. Perfect systems. Compositio Mathematica, Tome 19 (1968) no. 2, pp. 95-166. http://www.numdam.org/item/CM_1968__19_2_95_0/

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