(Al Jazeera English News Headlines: May 20, 2010) Greeks continue to protest tax increases and cuts in pay and pensions, instituted by the Greek government to combat its massive debt problems. In South Korea, international investigators said that a North Korean submarine sunk a South Korean warship in March, sparking anger in the South. Picasso and Matisse paintings valued at over $630 million have been stolen from the Paris Museum of Modern Art.