Ajiro Tatsuhiko and Warita Ikuo, Waga kuni no kōiki na chimei oyobi sono han'i ni tsuite no chōsa kenkyū (The geographical names and those extents of the wide areas in Japan), Kaiyō Jōhōbu Gihō, Vol. 27, 2009.online editionArchived 2019-05-18 at the Wayback Machine
Ajiro Tatsuhiko and Warita Ikuo, Waga kuni no kōiki na chimei oyobi sono han'i ni tsuite no chōsa kenkyū (The geographical names and those extents of the wide areas in Japan), Kaiyō Jōhōbu Gihō, Vol. 27, 2009.online editionArchived 2019-05-18 at the Wayback Machine