WASET
    Ivanova B. Natalia and  Djambova ΠΆ. Svetlana and  Hristev S. Ivailo,  Investigation of the Acoustic Properties of Recycled Felt Panels and Their Application in Classrooms and Multi-Purpose Halls.   journal   = {International Journal of Civil and Environmental Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2024, vol. 208(4). 184 - 187
    [viewed 17 May 2024]. Available from: https://publications.waset.org/pdf/10013617.