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3. The use of oxygen microprobes to measure bacterial respiration for determining bacterioplankton growth efficiency
4. Dimkov R., Topalova Y. (2003) Regulation of Biodegradation Processes, 1stEd., Sofia, Sofia, p. 224. (In Bulgarian)
5. Ilieva L. (1999) Management of the environment, 1stEd., Tilia Publishing, Sofia, p. 115. (In Bulgarian)