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Ostlund HG 《Science (New York, N.Y.)》1957,126(3272):493-497
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Wilding LP 《Science (New York, N.Y.)》1967,156(3771):66-67
Approximately 75 grams of biogenetic opal were isolated from 45 kilograms of soil by employing gross particle-size and sink-float specific gravity fractionation procedures. After pretreatment of the sample to remove extraneous organic and inorganic carbon contaminants, the carbon occluded within opal phytoliths was dated at 13,300 +/- 450 years before the present. Therefore, biogenetic opal is stable for relatively long periods. 相似文献
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Tauber H 《Science (New York, N.Y.)》1956,124(3227):879-881
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