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Views and attitudes of Burgas's residents (Bulgaria) for paper recycling
Arabatzis, Garyfallos, (2014)
Okrǔžnata kompleksna programa, osnova i sredtvo za upravlenie na naučno-techničeskija progres
Čavdarova, Deljana, (1982)
Burgas
Penkov, Ignat Ignatov, (1968)