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This is to certify that your paper entitled «Exposure and risk assessment of PAHs in indoor air of waterpipe cafés in Ardebil, Iran» was indexed with 1 pages, in the CIVILICA citation database, code COI:NCOHS11_251, after evaluation and approval of the referees of the "Eleventh General Conference on Occupational Health and Safety held in Tehran 2020.

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.