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This is to certify that your paper entitled «Optimizing biogas production with synergetic effects of sewage sludge and sugarcane straw in anaerobic co-digestion with long-hydraulic retention time based on optimal-mixture design» was indexed with 19 pages, in the CIVILICA citation database, code COI:NCAMEM15_094, after evaluation and approval of the referees of the "The 15th National Congress and the First International Congress of Biosystem Mechanical Engineering and Agricultural Mechanization held in Tehran 2023.

While offering our congratulations on the indexation of your paper, please be informed that this certificate is prepared based on the information submitted by the secretariat of the above conference and the information contained in the CIVILICA database, and the accuracy of its content can be inquired at any time through link provided at the bottom of the page or scanning the code image.