Quotations from a text, whether print or electronic, can be a strong form of evidence of you properly cite the sources of all quotations that you include. During the note taking and pre-writing process, note the author's name, title of the text and the page number of the quote, so you can properly reference it in the text and works cited page. You can determine credibility of online sources by evaluating the date of publication and the author. Print newspapers, such as "The New York Times," and governmental organizations, such as the National Institutes of Health, offer credible sources.
Historical examples can provide background information and caution against or confirm a point. For example, if your essay is arguing that American society needs some degree of government assistance to thrive, you can cite President Roosevelt's New Deal as a historical example to support your thesis. Historical examples can show whether a policy, tradition or law did or did not work in the past; it is your responsibility to show how the example correlates to the main issue in your essay.
Facts such as statistics and charts are commonly employed as evidence in scientific papers, including those of the social and political sciences. When using quantifiable examples, provide a diverse range of evidence to show you have a developed understanding of the issue. Communication professor Phillip Howard of the University of Washington advises using multiple references to support a statistic. For every piece of data you present, interpret its significance for the reader, showing how it supports your thesis statement and affects the reader.
You cannot expect the evidence to do all the work for you. Analysis and explanation are needed to show how the evidence supports the topic sentence and the thesis statement of the essay. The University of North Carolina at Chapel Hill's Writing Center advises that the writer must clarify the link between the evidence and the essay's main argument. Even when the relationship between example and argument feels evident to you, write it out so the reader can see the same connections you do. This practice develops and strengthens the essay.