Submitted on: 06 January 2011.
Revised on: 15 February 2011.
Accepted on: 22 February 2011.
WMU Journal of Maritime Affairs
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Submitted on: 12 September 1998.
Revised on: 18 October 1998.
Accepted on: 14 November 1998.
WMU Journal of Maritime Affairs
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http://reply.papertrans.cn/4/307/30699/30699-35.png
Submitted on: 14 August 2010.
Revised on: 21 September 2010.
Accepted on: 07 October 2010.
WMU Journal of Maritime Affairs