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Submitted on: 10 January 2005.
Revised on: 15 April 2005.
Accepted on: 18 May 2005.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA
Submitted on: 10 March 2022.
Revised on: 02 July 2022.
Accepted on: 26 August 2022.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA
Submitted on: 16 June 2012.
Revised on: 27 September 2012.
Accepted on: 27 October 2012.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA
Submitted on: 24 November 2004.
Revised on: 08 January 2005.
Accepted on: 07 March 2005.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA
Submitted on: 20 August 2008.
Revised on: 16 November 2008.
Accepted on: 29 December 2008.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA
Submitted on: 20 March 2009.
Revised on: 07 May 2009.
Accepted on: 25 May 2009.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA
Submitted on: 23 December 2013.
Revised on: 14 March 2014.
Accepted on: 30 April 2014.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA
Submitted on: 22 January 2000.
Revised on: 13 February 2000.
Accepted on: 27 February 2000.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA
Submitted on: 16 May 2018.
Revised on: 13 July 2018.
Accepted on: 13 August 2018.
___________________CUBO-A Mathematical Journal---UNIV FRONTERA, DEPT MATEMATICA & ESTADISTICA