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Submitted on: 25 October 2017.
Revised on: 16 January 2018.
Accepted on: 17 February 2018.
___________________Epohi---ST CYRIL AND ST METHODIUS UNIVERSITY PUBLISHING HOUSE
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Submitted on: 11 March 2022.
Revised on: 21 June 2022.
Accepted on: 15 July 2022.
___________________Epohi---ST CYRIL AND ST METHODIUS UNIVERSITY PUBLISHING HOUSE
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Submitted on: 08 January 2017.
Revised on: 24 April 2017.
Accepted on: 23 June 2017.
___________________Epohi---ST CYRIL AND ST METHODIUS UNIVERSITY PUBLISHING HOUSE
Submitted on: 05 May 2009.
Revised on: 08 August 2009.
Accepted on: 05 September 2009.
___________________Epohi---ST CYRIL AND ST METHODIUS UNIVERSITY PUBLISHING HOUSE