"山極 勝三郎" [Katsusaburō Yamagiwa]. Nihon Jinmei Daijiten (in Japanese). Tokyo: Shogakukan. 2012. Archived from the original on August 25, 2007. Retrieved November 8, 2012.
姉妹都市・友好都市 (in Japanese). Archived from the original on October 25, 2007. Retrieved November 3, 2007.
"山極 勝三郎" [Katsusaburō Yamagiwa]. Nihon Jinmei Daijiten (in Japanese). Tokyo: Shogakukan. 2012. Archived from the original on August 25, 2007. Retrieved November 8, 2012.