Submitted on: 11 November 2010.
Revised on: 21 December 2010.
Accepted on: 19 January 2011.
___________________Communications in Combinatorics and Optimization
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Submitted on: 02 April 2005.
Revised on: 30 July 2005.
Accepted on: 17 September 2005.
___________________Communications in Combinatorics and Optimization
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Submitted on: 21 February 2018.
Revised on: 18 June 2018.
Accepted on: 15 July 2018.
___________________Communications in Combinatorics and Optimization
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Submitted on: 15 April 1999.
Revised on: 01 August 1999.
Accepted on: 16 September 1999.
___________________Communications in Combinatorics and Optimization