IMPORTANT NOTE by Vukman Bakić, Editor-in-Chief of the journal Thermal Science Retraction Editor-in-Chief of the journal Thermal Science request that it is necessary to retract paper ANALYSIS OF PERIODIC HEAT TRANSFER THROUGH EXTENDED SURFACES DOI: https://doi.org/10.2298/TSCI220502184H by Kazal HAQ, Kamal SHAH, and Thabet ABDELJAWAD published in the journal Thermal Science, No.4A, Vol. 27, pp. 2623 - 2637, Year 2023, since by technical error of the Editorial staff, this paper has already been published in the journal Thermal Science Vol.27, No 3B, pp. 2549 - 2564, 2023 https://doi.org/10.2298/TSCI220502184H