@article{oai:u-ryukyu.repo.nii.ac.jp:02006918,
 author = {Maehara, Hiroshi and 前原, 潤},
 issue = {14},
 journal = {琉球大学理工学部紀要. 理学編, Bulletin of Science & Engineering Division, University of Ryukyus. Mathematics & natural sciences},
 month = {Apr},
 note = {紀要論文},
 pages = {3--7},
 title = {On orbit spaces of semi-free SO(2) actions},
 year = {1971}
}