AZUZ (voice-over): Ten-second trivia: In the 1950s and 1960s, America's Project Blue Book studied what?
10秒钟冷知识速答：在20世纪50年代和60年代，美国的蓝皮书计划研究了什么？
跟马修学英语
Project Grudge, Project Blue Book, and all studies supposedly ended by 1970.
怨恨计划、蓝皮书计划和所有据称在 1970 年结束的研究。
中文百科
蓝皮书计划
蓝皮书计划（Project Blue Book）是美国空军为调查不明飞行物（UFO）而成立的研究计划。
成立于1952年，于1969年12月被命令终止，但持续活动到1970年1月。
英语百科
Project Blue Book 蓝皮书计划
Project Blue Book was one of a series of systematic studies of unidentified flying objects (UFOs) conducted by the United States Air Force. It started in 1952, and it was the third study of its kind (the first two were projects Sign (1947) and Grudge (1949)). A termination order was given for the study in December 1969, and all activity under its auspices ceased in January 1970.