Lillienberg L, Zock JP, Kromhout H, Plana E, Jarvis D, Toren K. A population-based study on welding exposures at work and respiratory symptoms. Ann Occup Hyg. 2008 Mar;52(2):107-15.
Michels KB, Rothman KJ. Update on unethical use of placebos in randomised trials. Bioethics. 2003 Apr;17(2):188-204.