Roentgen (R) 4 : A unit of exposure to ionizing radiation. It is that amount of gamma or x-rays required to produce ions carrying 1 electrostatic unit of electrical charge in 1 cm3 of dry air under standard conditions
US Army Center for Health Promotion and Preventive Medicine CHPPM, TG 204 Glossary of Terms For Nuclear, Biological, and Chemical Agents And Defense Equipment (Section 3 - Nuclear Terms), MD, USA 2001. http://www.au.af.mil/au/awc/awcgate/army/tg204.pdf , (Def Equip/ Nucl Terms - Amer) {488}
Madison County North Carolina Government, Madison County Emergency Operations Plan Glossary (Section 3: Nuclear Terms), NC, USA 2009. http://www.madisoncountync.org/eop/Madison_EOP_PDF /Glossary.pdf, (CBRNEmr - Amer) {875}