ワニエ関数
Karin M Rabe; Jean-Marc Triscone; Charles H Ahn (2007). Physics of Ferroelectrics: a Modern Perspective. Springer. p. 2. ISBN 3-540-34590-6. https://books.google.com/books?id=CWTzxRCDJdMC&pg=PA43&dq=%22Berry+connection%22#PPA2,M1