Zetra, Yulfi, et al. “Synthesis of 2-Hidroxyethyl Ester (2-HEE) and 2-Hydroxypropyl Ester (2-HPE) from Castor Oil As Bioadditives to Improve the Cold Flow Characteristic of Biodiesel”. Automotive Experiences, vol. 9, no. 1, May 2026, pp. 238-56, https://doi.org/10.31603/ae.15860.