The field of definition of the Mordell-Weil group of an elliptic curve over a function field
Compositio Mathematica, Tome 76 (1990) no. 3, p. 399-406 
@article{CM_1990__76_3_399_0,
     author = {Kuwata, Masato},
     title = {The field of definition of the Mordell-Weil group of an elliptic curve over a function field},
     journal = {Compositio Mathematica},
     publisher = {Kluwer Academic Publishers},
     volume = {76},
     number = {3},
     year = {1990},
     pages = {399-406},
     zbl = {0731.14010},
     mrnumber = {1080009},
     language = {en},
     url = {http://www.numdam.org/item/CM_1990__76_3_399_0}
}

Kuwata, Masato. The field of definition of the Mordell-Weil group of an elliptic curve over a function field. Compositio Mathematica, Tome 76 (1990) no. 3, pp. 399-406. http://www.numdam.org/item/CM_1990__76_3_399_0/

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