Dutch museums on Tuesday published two pages of Anne Frank's diary that had previously been hidden behind a layer of sticky brown paper.
The Anne Frank House Museum said at a presentation that it, and several Dutch historical institutes, were able to reproduce the lost pages after years of study by shining a light through them and photographing them in high resolution.
The Jewish teenager apparently covered up the pages because she worried that other people in her hideout would read them, as they contain a series of dirty jokes and her thoughts on sex education, said Ronald Leopold, director of Anne Frank House in Amsterdam.
Frank and her family hid from the Nazis in a secret annex in a house in Amsterdam during World War II but were discovered in 1944.
She died aged 15 at Bergen-Belson concentration camp in 1945. Her diary was published two years later and has been read worldwide and translated into at least 60 languages.