1. Surveys of radon levels in homes by University of Pittsburgh Radon Project;Cohen,1990
2. Variation of radon levels in U.S. homes with various factors;Cohen;J. Air Pollut. Contr. Assoc.,1988
3. Equivalent uranium map of the conterminous United States;Duval,1989
4. Residential radon survey of twenty-three States;Dziuban,1990
5. Sensitivity of soil radon to geology and the distribution of radon and uranium in the Hylas zone area, Virginia;Gates,1992