I V, Starostina, et al. “Efficient Carbonaceous Sorbent Based on the Waste Sludge of Oil Extraction Industry for Purifying Wastewater from Petroleum Products”. International Journal of Engineering & Technology, vol. 7, no. 2.23, Apr. 2018, pp. 266-9, https://doi.org/10.14419/ijet.v7i2.23.11928.