Event:
Pope Pius XII publishes encyclical Mediator Dei
More Notable Events on November 20:
1986 UN's WHO announces 1st global effort to combat AIDS
1984 McDonald's made its 50 billionth hamburger
1975 Ronald Reagan announced candidacy for Republican nomination for president
1967 U.S. population reaches 200 million
1914 U.S. State Department starts requiring photographs for passports
