Other Notable Events, April 6

In 1973, American League baseball teams used a designated hitter for first time.

In 1991, Iraq's Parliament accepted a permanent cease-fire in the Gulf War.

In 1992, science fiction patriarch Isaac Asimov, 72, died after a lengthy illness.

In 1994, the presidents of the African nations of Rwanda and Burundi were among people killed in a plane hit by rockets as it tried to land in Kigali, Rwanda. (The attack triggered fighting between the Hutu and Tutsi ethnic groups that left hundreds of thousands of people dead in what became known as the Rwandan Genocide.)

In 1998, U.S. health officials announced that tamoxifen, a synthetic hormone, prevented breast cancer in women at high risk.

In 2004, the University of Connecticut became the first school to win both the NCAA Division I men's and women's college basketball championships the same year.

In 2005, Prince Rainier III of Monaco, one of Europe's longest-reigning monarchs, died from multiple organ failure at the age of 81. He was succeeded by Prince Albert, one of three children of Rainier and his wife, U.S. movie star Grace Kelly, who died after a car crash in 1982.

In 2007, a U.N.-sponsored scientific panel endorsed by 120 countries warned of dire consequences unless worldwide buildup in greenhouse gases was cut back.

In 2008, American Airlines grounded all 300 of its MD-80 jetliners after an FAA review found faulty wiring in nine of them. (Over the next five days, American canceled about 3,300 flights, disrupting travel of more than 100,000 passengers.)

In 2009, a 6.3-magnitude earthquake struck central Italy's Abruzzo region, killing more than 200 people and severely damaging the city of L'Aquila.

In 2011, Washington Gov. Chris Gregoire signed a bill under which the state would acknowledge same-sex marriages in other states as domestic partnerships.

In 2013, former South African President Nelson Mandela, 94, was sent home from a Johannesburg hospital after treatment for pneumonia. (Mandela later had an extended hospital stay and died at home in December.)