Freier, D., Ramirez-Iniguez, R., Jafry, T., Muhammad-Sukki, F., & Gamio, C. (2018). A review of optical concentrators for portable solar photovoltaic systems for developing countries. Renewable and sustainable energy reviews, 90, 957-968. https://doi.org/10.1016/j.rser.2018.03.039