I want to know the answer to the following question:
When did Xudong An and Anthony B. Sanders issue a report about commercial mortgage-backed securities?
All the background I'm provided with is that "After researching the default of commercial loans during the financial crisis, Xudong An and Anthony B. Sanders reported (in December 2010): "We find limited evidence that substantial deterioration in CMBS [commercial mortgage-backed securities] loan underwriting occurred prior to the crisis.". Is that enough to answer the question?