Yellen takes the stage; Samsung sentencing; Amazon in focus

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1. Jackson Hole: Two of the world's most important central bankers are speaking on Friday at the Jackson Hole economic symposium. Investors will be paying close attention.

Janet Yellen will speak at 10 a.m. ET in what could be her final appearance at the summit as leader of the Federal Reserve. President Trump could decide to reappoint her to another term in February, but many analysts think the White House will choose to go in another direction.

Mario Draghi, head of the European Central Bank, will follow at 3 p.m. Investors will be watching for signs of how the central bank plans to start winding down its stimulus program.

Central bankers have been known to announce major policy decisions at the forum.

2. Samsung sentencing: A South Korean court has found Lee Jae-yong, the de facto chief of the sprawling Samsung business empire, guilty of bribery and other corruption charges.

Lee, the billionaire son of Samsung's ailing chairman, was sentenced to five years in prison on Friday.

The criminal conviction is a blow for Samsung, the world's largest smartphone maker and South Korea's biggest family conglomerate.

The so-called "trial of the century" has gripped the country for months. It's part of a huge influence-peddling scandal that brought down the government of former President Park Geun-Hye. Park is also on trial.

Samsung Electronics' shares closed down 1.1% in Seoul following the verdict.

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3. Stock market overview: The past two days of trading have been muted and investors seem content with the summer lull.

U.S. stock futures were holding steady on Friday.

European markets posted small gains in early trading. Most Asian markets advanced, with Chinese indexes jumping by more than 1%.

On Thursday, the Dow Jones industrial average, S&P 500 and Nasdaq all dipped by 0.1% to 0.2%.

Investors will continue to monitor moves by Amazon (AMZN), which announced on Thursday that its takeover of Whole Foods (WFM) will close on Monday. It said its first order of business will be to make some groceries more affordable.

Items that will be marked down on Monday include organic avocados, organic brown eggs, almond butter and organic rotisserie chicken.

Shares in competing grocery chains including Kroger (KR) and Sprouts Farmers Market (SFM) plunged following the announcement but look set for a small rebound on Friday.

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4. Coming this week:

Friday -- Fed chair Janet Yellen speaks at 10 a.m.