9Gerhard P, Essen, Martin S, et al. Washing agent and a process for washing acidic components from a gas stream: US, 3773896[P]. 1973-11-20.
10Pohler, Joachim, Modle, et al. Method for reprocessing waste oils, base oils abtained according to said method and use thereof: CA, 2351606[P]. 2001-05-10.