Democratic Senator Bernie Sanders dropped out of the race for US president.
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Researchers discovered that as many as 600 million birds die in the US every year after flying into skyscrapers.
One of the world's most important medieval castles, Krak des Chevaliers, was conquered by Sultan Baibars.
The first person in the world to be diagnosed with Alzheimer's died.
German mathematician Carl Friedrich Gauss became the first person to prove quadratic reciprocity law.
Clint Eastwood was elected as Mayor of Carmel, California.
