Wald N J, Chamberlain J, Hackshaw A
Department of Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, St Bartholomew's Hospital Medical College, London, UK.
Clin Oncol (R Coll Radiol). 1994;6(4):261-8. doi: 10.1016/s0936-6555(05)80298-5.