主题：【已应助】求助几篇文献。谢谢啦！

【序号】：1
【作者】：Krukowski, S.T.
【题名】：Sodium metatungstate: a new heavy-mineral separation medium for extraction of conodonts from insoluble residues
【期刊】：Journal of Paleontology
【年卷期】：March 1988; v. 62; no. 2; p. 314-316
【全文链接】http://jpaleontol.geoscienceworld.org/cgi/content/abstract/62/2/314

【序号】：2
【作者】：Brasier MD, Green OR, Jephcoat AP, Kleppe AK, Van Kranendonk MJ, Lindsay JF, Steele A, Grassineau NV.
【题名】：Questioning the evidence for earth’s oldest fossils
【期刊】：Nature
【年卷期】：2002 Mar 7;416(6876):76-81.
【全文链接】http://www.nature.com/nature/journal/v416/n6876/abs/416076a.html

【序号】：3
【作者】：Christopher H. House, J. William Schopf， Kevin D. McKeegan, Christopher D. Coath, T. Mark Harrison and Karl O. Stetter
【题名】：Carbon isotopic composition of individual Precambrian microfossils
【期刊】：Geology;
【年卷期】：August 2000; v. 28; no. 8; p. 707-710
【全文链接】http://geology.geoscienceworld.org/cgi/content/abstract/28/8/707