Researchers discovered that as many as 600 million birds die in the US every year after flying into skyscrapers.
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Democratic Senator Bernie Sanders dropped out of the race for US president.
The Iron Lady Margaret Thatcher died at 87 years old.
The first idea of a fire escape was patented.
German mathematician Carl Friedrich Gauss became the first person to prove quadratic reciprocity law.
Roman Emperor Caracalla was stabbed to death by a guard while urinating.
