@article{oai:tsukuba.repo.nii.ac.jp:00016902, author = {Hirano, T. and Katsura, H. and 初貝, 安弘 and HATSUGAI, Yasuhiro}, issue = {5}, journal = {Physical review B}, month = {Aug}, title = {Degeneracy and consistency condition for Berry phases: Gap closing under a local gauge twist}, volume = {78}, year = {2008}, yomi = {ハツガイ, ヤスヒロ} }