For example, if you are borrowing a quotation of Smith's work, which is cited in Jones:
In Text
Name the original source in the sentence, and provide an in-text citation for the secondary source. Include the abbreviation qtd. in to indicate that you are citing a quotation:
According to Smith's research (qtd. in Jones 12)...
Work Cited
Include the source you actually read in your Works Cited. As you read Jones, not Smith, include Jones in your Works Cited list.