Stocks: 4 things to know before the open

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Markets are dipping again Tuesday following a negative start to the week.

Here are the four things you need to know before the opening bell rings in New York:

1. Stock market overview: U.S. stock futures are looking a bit weak ahead of the open.

European markets are mostly declining in early trading. The majority of Asian markets ended with losses.

On Monday, the Dow Jones industrial average, the S&P 500 and the Nasdaq each shed 1%.

Related: Fear & Greed Index

2. Eyes on Europe: Investors are warily eying developments in Europe.

U.K. Prime Minister David Cameron is outlining plans to renegotiate the country's membership in the European Union. Britain is slated to have a referendum by 2017 to decide whether to remain in the EU or break away altogether. Investors are concerned about the many unknowns involved with a "Brexit."

The Portuguese parliament is holding a vote that will decide the fate of Prime Minister Pedro Passos Coelho. It's widely expected he'll be ousted by left-wing opponents who are challenging Portugal's commitment to austerity.

And Greece's latest bailout payment of 2 billion euros ($2.2 billion) has been delayed by European officials who say the country isn't making enough progress with agreed reforms.

3. Stock market mover: Gap (GPS) shares are sinking about 5% in extended trading after the retailer posted its latest earnings update. The company, which also owns the Old Navy and Banana Republic brands, has been hurting for years and recently lost a prized executive to Ralph Lauren (RL).

4. Not-so-fast food: Expect long lines and slower service at McDonald's (MCD) and Burger King as workers warn they will be holding a massive strike to call attention to low wages. They are calling for a new minimum wage of $15 per hour and union rights.

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