![]() ![]() to the point that some people call them tertiary sources. Primary or Secondary SourcesĪs compilations of existing information, reference works are decisively in the category of secondary sources. Check your style manual for best guidelines. ![]() In fact, because they mostly contain established, factual information, they're sometimes not even cited in academic works, unless directly quoted. Reference sources are rarely peer-reviewed. ![]() Because print-only reference books are in high demand, they are kept in separate, non-circulating reference collections in most UCLA libraries. Many reference works are available online and are accessible through links from the Library Catalog and from subject or course guides, but many valuable reference resources are still available only in print, and a few highly specialized tools are on microform or CD. But they're also where you return when you need to look up formulas, facts, definitions, and other standard details they tend to pack a lot of information into simple, easy-to-use packages. Reference sources are generally the place to begin your research, especially when you're starting out with an unfamiliar field. Recommendations for more detailed sources (like books and articles).Basic overviews of new subjects when you're getting started.Repeat for each source that has contributed to your work. Copy your new reference from the citation generator into your bibliography or works cited list. Click the ‘Cite’ button on the citation machine. The calibration approach of the mixed EARTHTIME 235U–233U–205Pb(–202Pb) tracers, in addition to updated values for reference materials (e.g., mixed gravimetric reference solutions), and parameters (e.g., Pb reference material assay), can be applied to other laboratory-specific U–Pb tracers and will facilitate the generation of accurate and directly inter-comparable U–Pb data.Summaries of facts, definitions, histories, statistics, and other types of information on large subject areas, organized for quick lookup. Enter the URL, DOI, ISBN, title, or other unique source information into the citation generator to find your source. For suitable terrestrial materials such as zircon, when other sources of uncertainty have been minimised (e.g., open-system behaviour, 238U/235U variation, intermediate daughter product disequilibrium, common Pb, etc.) the U–Pb tracer calibration uncertainty is a limiting factor in the accuracy of U–Pb geochronology – but less so than the uncertainty in the 238U and 235U decay constants (☐.11 and 0.14% 2σ). The parameters used in calculating U/Pb ratios (and inferentially U–Pb dates) have correlated uncertainties that result in a total uncertainty contribution to 206Pb/238U dates of ± < 0.03% (95% confidence). Facies and thickness of units change rapidly across the. The accuracy of the EARTHTIME U–Pb tracer isotopic composition can be traced back to SI units via a series of assay and isotopic composition reference materials combined with the experiments described herein. Locally, striated pebbles and dropstones indicate a glacial origin of some of the diamictites (12). The methods and results for the preparation and calibration of the U/Pb ratio and isotopic abundances are given, and the various sources of uncertainty are discussed and quantified. Mixed 235U–233U–205Pb(–202Pb) tracers for U–Pb isotope-dilution isotope ratio mass spectrometry have been prepared under the auspices of the EARTHTIME Initiative.
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