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Submitted on: 23 March 2008.
Revised on: 04 April 2008.
Accepted on: 12 April 2008.
Open Mathematics---DE GRUYTER POLAND SP Z O O
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Submitted on: 06 March 2016.
Revised on: 07 April 2016.
Accepted on: 21 April 2016.
Open Mathematics
Submitted on: 04 April 2009.
Revised on: 07 May 2009.
Accepted on: 17 May 2009.
Open Mathematics
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Submitted on: 29 July 1998.
Revised on: 23 August 1998.
Accepted on: 18 September 1998.
Open Mathematics
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