Submitted on: 03 June 2001.
Revised on: 15 July 2001.
Accepted on: 29 July 2001.
PHYSICS LETTERS B---ELSEVIER
Submitted on: 10 June 2011.
Revised on: 24 June 2011.
Accepted on: 05 July 2011.
PHYSICS LETTERS B
Submitted on: 13 July 2012.
Revised on: 28 July 2012.
Accepted on: 25 August 2012.
PHYSICS LETTERS B
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Submitted on: 08 November 2000.
Revised on: 27 November 2000.
Accepted on: 06 December 2000.
PHYSICS LETTERS B---ELSEVIER