Which of the following sentences in a research paper should include a citation?

Question

Quizplus · Accepted Answer

Writers need to include citations when using data, ideas, images, etc. that are not their own (including paraphrasing of ideas). Information that would not be considered common knowledge should also receive citations for its source. In this example, the writer wants to include data collected by the U.S. Department of Agriculture, which would need a citation because it is data coming from a source other than the writer.
Keeping in mind the data from the U.S. Department of Agriculture on soybean crops mentioned in the introduction of this paper, we conclude that more research is needed if we want to find a cheaper way to feed livestock. This does not require a citation, as it is a conclusion that the authors of the paper have reached on their own and was not taken from a different source of information.
This paper examines the role of soybeans in modern agriculture. This sentence is simply stating the purpose of the paper and does not require a citation.
Soybean meal is a significant and cheap source of protein for animal feeds. This sentence would be considered "common knowledge" because it is information that we can accept as fact without requiring a reference to a source to prove it is true.

Which of the Following Sentences in a Research Paper Should