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Submitted on: 17 November 2016.
Revised on: 20 February 2017.
Accepted on: 27 March 2017.
___________________Annals of the University of Craiova-Mathematics and Computer Science Series
Submitted on: 07 October 2013.
Revised on: 04 January 2014.
Accepted on: 22 February 2014.
___________________Annals of the University of Craiova-Mathematics and Computer Science Series
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Submitted on: 15 March 2017.
Revised on: 05 July 2017.
Accepted on: 20 July 2017.
___________________Annals of the University of Craiova-Mathematics and Computer Science Series
Submitted on: 04 August 2022.
Revised on: 10 September 2022.
Accepted on: 04 November 2022.
___________________Annals of the University of Craiova-Mathematics and Computer Science Series
Submitted on: 26 March 2024.
Revised on: 12 July 2024.
Accepted on: 04 September 2024.
___________________Annals of the University of Craiova-Mathematics and Computer Science Series
Submitted on: 25 September 2012.
Revised on: 11 December 2012.
Accepted on: 06 February 2013.
___________________Annals of the University of Craiova-Mathematics and Computer Science Series