As oil sinks, some companies float idea of 'zero clause' in trades

LONDON/NEW YORK (Reuters) - After the worst quarter for oil prices in history, some oil producers have begun to include protection in their contracts to avoid being forced to pay buyers for the oil they pump if prices slide below $0 a barrel.Crude prices in key physical markets - including the United States, Canada, Mexico and Europe - have fallen through $10 a barrel, far below comparable futures prices, as demand slumps and storage fills. Those discounts could widen even further, making it..