Masahiro Hamano, Mitsuhiro Okada. A direct independence proof of Buchholz s Hydra Game on finite labeled trees. Arch. Math. Log., 37(2):67-89, 1998. [doi]
@article{HamanoO98,
title = {A direct independence proof of Buchholz s Hydra Game on finite labeled trees},
author = {Masahiro Hamano and Mitsuhiro Okada},
year = {1998},
doi = {10.1007/s001530050084},
url = {http://dx.doi.org/10.1007/s001530050084},
researchr = {https://researchr.org/publication/HamanoO98},
cites = {0},
citedby = {0},
journal = {Arch. Math. Log.},
volume = {37},
number = {2},
pages = {67-89},
}