In addition to summarizing a single source, writers often summarize groups of sources. Such collective summaries (often introduced by phrases such as “Numerous authors argue . . .” or “The research in this area seems to indicate that . . .”) allow you to establish a point briefly and with authority. They are particularly effective at the beginning of a document, when you are establishing the nature of the conversation you are joining, and can serve as a transitional device when you move from one major section of the document to another.

When you summarize a group of sources, separate the citations with a semicolon. MLA guidelines require including author and page information, as in the following example.

Several critics argue that the Hemingway code hero is not always male (Graulich 217; Sherman 78; Watters 33).

In APA style, the author and the date of publication must be included.

The benefits of early detection of breast cancer have been well documented (Page, 2011; Richards, 2013; Vincent, 2012).