1. About UL | UL. (n.d.). Retrieved May 23, 2021, from https://www.ul.com/about
2. Dumlu, L. (2014). Kağıt Endüstrisi Atık Sularına Uygun Arıtma Teknolojilerinin Belirlenmesi ve Türkiye’deki Mevcut Durumun Analizi (Çevre ve Şehircilikbakanliği Çevre Yönetimi Genel Müdürlüğü). Retrieved from https://webdosya.csb.gov.tr/db/destek/icerikler/lutf-ye_dumlu_uzmanl-k_tez%2D%2D20191127122356.pdf
3. EPEAT. (n.d.). About EPEAT | EPEAT Registry. Retrieved May 23, 2021, from https://www.epeat.net/about-epeat
4. Green Seal. (n.d.). About Us | Green Seal. Retrieved May 23, 2021, from https://greenseal.org/about/
5. Harley, G., Timmis, A., & Budd, L. (2020). Factors affecting environmental practice adoption at small European airports: An investigation. Transportation Research Part D: Transport and Environment, 88, 102572. https://doi.org/10.1016/j.trd.2020.102572