Submitted on: 15 December 2002.
Revised on: 13 February 2003.
Accepted on: 27 February 2003.
___________________Electronic Markets---SPRINGER HEIDELBERG
Submitted on: 24 March 2001.
Revised on: 10 June 2001.
Accepted on: 07 July 2001.
___________________Electronic Markets---SPRINGER HEIDELBERG
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Submitted on: 01 July 2007.
Revised on: 24 September 2007.
Accepted on: 09 November 2007.
___________________Electronic Markets---SPRINGER HEIDELBERG
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Submitted on: 22 December 2010.
Revised on: 04 February 2011.
Accepted on: 28 March 2011.
___________________Electronic Markets---SPRINGER HEIDELBERG
Submitted on: 28 July 2017.
Revised on: 15 November 2017.
Accepted on: 04 December 2017.
___________________Electronic Markets---SPRINGER HEIDELBERG