@article{oai:tsukuba.repo.nii.ac.jp:00016032,
 author = {Koike, Naoyuki},
 issue = {1},
 journal = {Tsukuba Journal of Mathematics},
 month = {Jun},
 pages = {267--286},
 title = {On tubes of nonconstant radius},
 volume = {17},
 year = {1993}
}