AMSTERDAM (AP) — Researchers using digital photo editing techniques have managed to read the text on two pages from Anne Frank's world famous wartime diary that the teenager had covered with brown masking paper, revealing risque jokes and an explanation of sex and prostitution.

The Anne Frank Foundation announced the discovery Tuesday, saying it helps to explain her adolescent interest in sexuality.

Anne Frank House museum executive director Ronald Leopold, says that "like every adolescent she is curious about this subject," adding that Anne wrote about the subject elsewhere in diary pages that already have been published.

Anne wrote her diary while she and her family hid for more than two years in a secret annex behind an Amsterdam canal-side house in an attempt to avoid Nazi occupiers during World War II.