I normally refer to the UNSCEAR series of documents for up-to-date references. They are readily available and cover the world's scientific literature. John R Johnson, PhD Scientist Emeritus, HPD/PNNL President and CEO, IDIAS 2629 Harris Richland, WA, 99352 e:mail; jr_johnson@pnl.gov Phone: (509) 375-6850 (PNNL) Phone: (509) 375-3005 (IDIAS) FAX: (509) 375-2019 (PNNL)