Apple Newsroom. (2018). Apple paves the way for breakthrough carbon-free aluminum smelting method. [online] Available at: https://www.apple.com/newsroom/2018/05/apple-paves-the-way-for-breakthrough-carbon-free-aluminum-smelting-method/.

u.osu.edu. (n.d.). Extraction of Raw Materials | iPhone Commodity Chain. [online] Available at: https://u.osu.edu/iphonecommoditychainproject/extraction-of-raw-materials/.

u.osu.edu. (n.d.). Manufacturing | iPhone Commodity Chain. [online] Available at: https://u.osu.edu/iphonecommoditychainproject/manufacturing/.