affidavit
n
(law 律) written statement that can be used as evidence in court, made by sb who swears that it is true (宣誓属实可用作法庭证据的)书面证词; 宣誓书
swear/make/take/sign an affidavit 订立[签署]宣誓书.
Professor Karl von Frisch, an Austrian scientist, spent many years of his life researching the amazing ways honey bees communicate in their dark hives.