In 1963, negotiations between East and West resulted in a limited possibility for visits during the Christmas season that year (Passierscheinregelung). Similar very limited arrangements were made in 1964, 1965 and 1966. In 1971, with the Four Power Agreement on Berlin, agreements were reached that allowed West Berliners to apply for visas to enter East Berlin and East Germany regularly, comparable to the regulations already in force for West Germans.