Answer:
Inform the audience of the author or origin of any information that is not common knowledge.
Explanation:
It would be hard to directly quote, during a speech, the pages or reference numbers of a source and not lose the audience's attention, not to mention that, if it's common knowledge, they may think that are being made look like fools.
This way you can quote authors and ideas or references whilst having a smooth speech.
The other option, arranging information in your own words, is plagiarism.
