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This is to certify that your paper entitled «Determination of ammonium in river water using the combination of paper-based analytical device and smartphone app» was indexed with 7 pages, in the CIVILICA citation database, code COI:JR_IJCOE-7-4_005, after evaluation and approval of the referees of the "International Journal of Coastal, Offshore and Environmental Engineering Vol 7, Issue 4 , Year 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 journal 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.