Connecting decision makers to a dynamic network of information, people and ideas, Bloomberg quickly and accurately delivers business and financial information, news and insight around the world. Eleven months of depressed oil prices are threatening to topple more companies in the energy industry. Four firms owing a combined $4.8 billion warned this week that they may be at the brink, with Penn Virginia Corp., Paragon Offshore Plc, Magnum Hunter Resources Corp. and Emerald Oil Inc. saying their auditors have expressed doubts that they can continue as going concerns. Falling oil prices are squeezing access to credit, they said....