United States Government Accountability Office
Virtual Economies and Currencies:
Additional IRS Guidance Could Reduce Tax Compliance Risks
GAO-13-516, May 15, 2013
released on Jun 17, 2013
http://gao.gov/products/GAO-13-516
Direct link:
http://gao.gov/assets/660/654620.pdf
txt version:
http://gao.gov/assets/660/655226.txt

Audio interview by GAO staff with Jim White, Director,
Strategic Issues on Related GAO Work: GAO-13-516
http://www.gao.gov/assets/660/654443.txt