http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Maximum ages of the Côa valley (Portugal) engravings measured with Chlorine-36
Panel faces in teh Côu valley, Portugal, were available for engraving during the Upper Palaeolithic, according to 36Cl exposure ages of 16,000 to 136,000 years.