Researchers using digital editing techniques deciphered the writing on two pages of Anne Frank's diary that she had covered over with brown masking paper, discovering four risque jokes and a candid explanation of sex, contraception and prostitution. She wrote the recently discovered pages on September 28, 1942 at the age of 13, about three months after the Frank family went into hiding, and later covered them up with brown paper, the Associated Press reports.
Mystery has swirled around the two pages of Anne Frank's diary where brown paper was pasted over the writing.
"Anne's diary texts show that she had gleaned information on the subject of sexuality from her parents, especially her father, from her friend Jacqueline and from books", the statement reads.
The pages' content had remained unknown for decades because Frank had erased them.
Experts believe the text revealed more about Miss Frank's as a writer, rather than about her interest in sex.
Thanks to modern image processing technology, the writing from 1942 was uncovered, and four "dirty jokes" appeared. The Frank family lived in a modest brick building from 1934 in the Dutch capital, after fleeing rising anti-Semitism in neighbouring Germany, until they went into hiding.
He said the jokes "make it clear that Anne, with all her gifts, was above all also an ordinary girl".
She had been in a hidden annexe for two months, hiding from the Nazi occupiers of Amsterdam with her family and another Jewish family. The family was provided with food and other essentials by a close-knit group of helpers, until 4 August 1944 when they were discovered and ultimately deported to Auschwitz.
In a snippet of the text, she explains how women get their periods around 14 years of age, and said it "a sign that she is ripe to have relations with a man but one doesn't do that of course before one is married".
About prostitution, Anne wrote: "All men, if they are normal, go with women, women like that accost them on the street and then they go together".
The Anne Frank House addressed moral considerations in deciphering a text that its author did want read. Only Anne Frank's father, Otto, survived the Holocaust.
He added that the adolescent had also written about the subject in several other pages of her diary, which have already been published.
Miss Frank and her sister died in camp, when she was just 15.