Georgiev, Venelin. ??????? ? ???????, ???????? ? ?????????? ??????????? ?? ?????????? ?? ???????? ?? ?????????????? ??????????? ?? ??????????? ???? ?? ????????? ???????? 2032 In CSDM Views., 2021.

???????, ??????. ???????????? ???????? ?? ????????? ????????: ???????? ?????? In ?????????? ?? ??????????? ? ?????????. Vol. 7. ?????: ??????, 2020.

Ratchev, Valeri. ????????? ?????? ?? ??????????? ?? ????????? 2014: ????? ????? ? ????? ??????????? ????? In CSDM Views. ?????: ?????? ?? ?????????? ?? ??????????? ? ?????????, 2015.