Ordinal analysis of bar recursion of type zero
Compositio Mathematica, Volume 42 (1980) no. 1, p. 105-119 
@article{CM_1980__42_1_105_0,
     author = {Howard, W. A.},
     title = {Ordinal analysis of bar recursion of type zero},
     journal = {Compositio Mathematica},
     publisher = {Sijthoff et Noordhoff International Publishers},
     volume = {42},
     number = {1},
     year = {1980},
     pages = {105-119},
     zbl = {0444.03030},
     mrnumber = {594485},
     language = {en},
     url = {http://www.numdam.org/item/CM_1980__42_1_105_0}
}

Howard, W. A. Ordinal analysis of bar recursion of type zero. Compositio Mathematica, Volume 42 (1980) no. 1, pp. 105-119. http://www.numdam.org/item/CM_1980__42_1_105_0/

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