Anne Frank tried to cover up two pages of writing in her diary that contained dirty jokes and a description of what she referred to as “sexual matters,” pasting brown paper over the pages in her red-and-white plaid notebook.

But researchers here have revealed the hidden text using new digital technologies, the Anne Frank House and two other Dutch cultural institutions announced on Tuesday.

Frank, the teenage diarist who wrote about coming-of-age in a secret attic annex while in hiding from the Nazis during World War II, may have camouflaged the two pages because they contained prurient content that she didn’t want her father or someone else in the cramped quarters to discover.