@article{oai:tsukuba.repo.nii.ac.jp:00016176,
 author = {Song, Hwa Hon Song and Kimura, Takahisa and Koike, Naoyuki},
 issue = {2},
 journal = {Tsukuba Journal of Mathematics},
 month = {Dec},
 pages = {263--280},
 title = {On proper helices and extrinsic spheres in pseudo-Riemannian geometry},
 volume = {20},
 year = {1996}
}