In the wake of the downgrade of Greeces national credit rating, demonstrators march on the streets of Athens yesterday to mark the first anniversary of the fatal shooting of a teenager by police, an incident that sparked massive riots. Standard and Poors hinted at downgrading Greece`s sovereign rating. European Central Bank President Jean-Claude Trichet said, "The situation in Greece is very difficult So this calls for very difficult, very courageous but absolutely necessary measures.