【题 名】：Sigma Convergence versus Beta Convergence: Evidence from U.S. County-Level Data
【作 者】： ANDREW T. YOUNG1, MATTHEW J. HIGGINS2, DANIEL LEVY3
【期刊、会议、单位名称】：Journal  of Money, Credit and Banking
【年, 卷(期), 起止页码】：Volume 40, Issue 5, pages 1083–1093, August 2008
【全文链接】：
http://onlinelibrary.wiley.com/doi/10.1111/j.1538-4616.2008.00148.x/full