Israel Warning Palastinians Before Bombing

BBC News - Are Israeli air strike warnings effective? -  Israel has urged thousands of people in east and north Gaza to leave their homes as it continues air strikes, which it says are aimed at stopping Hamas rocket attacks. Palestinian officials say at least 230 people have died in Israeli raids. Israel says it is trying to minimise civilian casualties by issuing a variety of warnings - but how effective are they? The BBC examines footage from both sides.