Submitted on: 21 August 2008.
Revised on: 12 October 2008.
Accepted on: 29 November 2008.
___________________ACTA INFORMATICA---SPRINGER
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Submitted on: 24 March 1999.
Revised on: 01 June 1999.
Accepted on: 15 July 1999.
___________________ACTA INFORMATICA---SPRINGER
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Submitted on: 13 July 2023.
Revised on: 08 September 2023.
Accepted on: 24 October 2023.
___________________ACTA INFORMATICA---SPRINGER
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Submitted on: 21 February 2005.
Revised on: 18 April 2005.
Accepted on: 02 May 2005.
___________________ACTA INFORMATICA---SPRINGER