@phdthesis{oai:tsukuba.repo.nii.ac.jp:00020794,
 author = {天野, 勝利},
 month = {},
 note = {2004, Includes bibliographical references},
 school = {筑波大学, University of Tsukuba},
 title = {Relative invariants, difference equations, and the Picard-Vessiot theory},
 year = {2005}
}