Submitted on: 02 May 2002.
Revised on: 15 June 2002.
Accepted on: 27 July 2002.
___________________JOURNAL OF PUBLIC ECONOMICS---ELSEVIER SCIENCE SA
Submitted on: 29 September 2004.
Revised on: 24 December 2004.
Accepted on: 14 January 2005.
___________________JOURNAL OF PUBLIC ECONOMICS---ELSEVIER SCIENCE SA
Submitted on: 07 June 2006.
Revised on: 13 August 2006.
Accepted on: 28 August 2006.
___________________JOURNAL OF PUBLIC ECONOMICS---ELSEVIER SCIENCE SA
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Submitted on: 23 February 2003.
Revised on: 30 March 2003.
Accepted on: 22 April 2003.
___________________JOURNAL OF PUBLIC ECONOMICS---ELSEVIER SCIENCE SA