To help you identify the sentence, here are some clues:
* Look for direct quotes: If a sentence includes a quote from a literary critic, historian, or other expert on Cooper, it's likely using outside resources.
* Check for citations: Look for references to specific books, articles, or websites. These are strong indicators of outside research.
* Notice phrases like "according to" or "as [expert] states": These phrases signal that the information is coming from another source.
Once you provide the sentences, I can help you determine which one is the most clear example of using outside resources.