@book{oai:u-ryukyu.repo.nii.ac.jp:02000885,
 author = {Maeda, Yoichi and Maehara, Hiroshi},
 month = {},
 note = {Volume title=Discrete and computational geometry : Japanese Conference, JCDCG 2002, Tokyo, Japan, December 6-9, 2002 : revised papers, 図書の1章},
 publisher = {Springer-verlag},
 title = {Observing an angle from various viewpoints},
 volume = {2866},
 year = {2003}
}