Ra-226 concentration in the vicinity of Ptolemais in Northern GreeceAnagnostakis et al., 1996 using data from the NTUA data set.
The same data is also referenced in:
United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)
Sources and Effects of Ionizing Radiation: Report to the General Assembly, with Scientific Annexes
ISBN 92-1-142200-0, United Nations, New York, 1993
The data set is available upon request