(1)A general test of the Prebisch–Singer hypothesis

Review of Development EconomicsVolume 3, Issue 1, pages 44–57, February 1999


http://onlinelibrary.wiley.com/doi/10.1111/1467-9361.00050/full


(2)
How well are long-run commodity price series characterized by trend components?
Journal of International DevelopmentVolume 17, Issue 4, pages 479–494, May 2005


http://onlinelibrary.wiley.com/doi/10.1002/jid.1139/abstract