Crusaders from the Fourth Crusade broke through Constantinople’s walls and entered the great city.
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Jonas Salk's Polio vaccine tested by Jonas Salk was given final approval by the US Food and Drug Administration.
The Battle of Fort Sumter in South Carolina between the United States and the Confederate States started the American Civil War.
The Zimbabwean dollar was suspended indefinitely.
Israeli Knesset chose April 13 as the official Holocaust Remembrance Day.
Hillary Clinton announced her candidacy for US President.
