Yang1, Jie, Weisong Kong1, Zhuiwen Cui1, Wei Liu1, Yongkuan Chen1, Guangyu Yang1, and Ping Ning1. 2011. “Ultrasonic Acid Digestion and Graphite Furnace Atomic Absorption Spectrometry for the Determination of Heavy Metal Ions in Tobacco”. Asian Journal of Chemistry 23 (5):1986-88. https://asianpubs.org/index.php/ajchem/article/view/10349.