Primarily, it is to avoid allegations of plagiarism and academic misconduct.
Secondarily, citing sources allows the reader to identify the sources that you relied on for your research.
It's easy: whenever you paraphrase the ideas of others, whenever you use a direct quotation, or whenever you cite a fact that isn't common knowledge, you need to cite your original sources, whether they are books, articles, lecture slides, material posted in Sakai, personal communications, or a web site.
The keys to successfully citing your sources in APA Style are:
This guide will walk you through the entire process of citing sources from creating in-text citations to your References list. It includes example citations from popular Business databases and statistics sources, as well as examples of how to cite audiovisual materials, and how to cite sources in your business presentations.