Submitted on: 21 November 2004.
Revised on: 12 March 2005.
Accepted on: 06 April 2005.
___________________CALCOLO---SPRINGER-VERLAG ITALIA SRL
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Submitted on: 26 January 2014.
Revised on: 21 February 2014.
Accepted on: 10 April 2014.
___________________CALCOLO---SPRINGER-VERLAG ITALIA SRL
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Submitted on: 03 April 2012.
Revised on: 24 May 2012.
Accepted on: 15 June 2012.
___________________CALCOLO---SPRINGER-VERLAG ITALIA SRL
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Submitted on: 29 November 1998.
Revised on: 01 January 1999.
Accepted on: 19 February 1999.
___________________CALCOLO---SPRINGER-VERLAG ITALIA SRL
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