@article{oai:tsukuba.repo.nii.ac.jp:00017155,
 author = {Kato, Takao and Keem, Changho and Ohbuchi, Akira},
 issue = {2},
 journal = {Tsukuba Journal of Mathematics},
 month = {Oct},
 pages = {421--441},
 title = {On triple coverings of irrational curves},
 volume = {21},
 year = {1997}
}