Wikipedia articles are usually footnoted with hypertext to a bibliographic "References" section. If you determine that the bibliographic source is reliable (see Evaluating Sources tab), you may want to obtain the source for your paper. Below is an annotated result from a search on "GPS."
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Selecting a footnote will take you to the References section:
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In this case the first footnote in the References section is a hyperlink to an external site:
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After the References section, there are often additional sections on "External Links" and "Further Reading:" These sites also need to be evaluated for usability, but they also may prove very valuable: