An article on CBC.ca reports that The YIVO Institute for Jewish Research recently discovered letters written by Otto Frank, revealing his efforts to move his family to safety during the Second World War. Anne Frank’s father wrote to friends and officials trying to obtain visas in order to escape to the U.S. or Cuba.

In 1942, the Frank family went into hiding in Amsterdam, where the Nazis discovered them two years later. Anne Frank’s diary, describing their time in hiding, has sold millions of copies and inspired several films and theatrical adaptations. The YIVO Institute plans to release the documents on Feb. 14. The Anne Frank Foundation has expressed interest in obtaining the letters for its archive.