Submitted on: 18 June 2001.
Revised on: 13 July 2001.
Accepted on: 16 August 2001.
___________________European Actuarial Journal---SPRINGER HEIDELBERG
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Submitted on: 03 April 2001.
Revised on: 30 June 2001.
Accepted on: 15 July 2001.
___________________European Actuarial Journal---SPRINGER HEIDELBERG
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Submitted on: 23 April 2018.
Revised on: 19 August 2018.
Accepted on: 12 September 2018.
___________________European Actuarial Journal---SPRINGER HEIDELBERG
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Submitted on: 15 May 2003.
Revised on: 09 September 2003.
Accepted on: 21 October 2003.
___________________European Actuarial Journal---SPRINGER HEIDELBERG