1. Foster, T.A. and Armstrong, R. 2006. The top 25 global 3PLs: is bigger really better? [online]. Global Logistics and Supply Chain Strategies. Available from: http://www.glscs.com/archives/05.06.25_3pls.htm?adcode=90.
2. Langley, C.J. Jr. 1996. Third-party logistics: key market/key customer study. The University of Tennessee and Exel Logistics.
3. Langley, C.J. Jr. 1997. Third-party logistics: key market/key customer study. The University of Tennessee and Exel Logistics.
4. Langley, C.J. Jr., Allen, G.R. and Colombo, M.J. 2003. Third-party logistics: results and findings of the 2003 eighth annual survey. Georgia Institute of Technology, Cap Gemini Ernst & Young and Federal Express Corp.
5. Langley, C.J. Jr., Allen, G.R. and Dale, T.A. 2004. Third-party logistics: results and findings of the 2004 ninth annual survey. Georgia Institute of Technology, Cap Gemini Ernst & Young and Federal Express Corp.