"河川法第四条第一項の水系を指定する政令" [River Law Clause 4 Paragraph 1: River System Designation Ordinance] (in Japanese). e-Gov.go.jp. Archived from the original on March 5, 2016. Retrieved July 6, 2016.
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"河川法第四条第一項の水系を指定する政令" [River Law Clause 4 Paragraph 1: River System Designation Ordinance] (in Japanese). e-Gov.go.jp. Archived from the original on March 5, 2016. Retrieved July 6, 2016.