Follow this link understand issues surrounding plagiarism.

In using secondary research, writers need to remember that knowledge develops socially in a give-and-take process akin to conversation. In this kind of social situation, it is a matter of both personal integrity and academic honesty to acknowledge others, especially when you use their words or ideas. Writers who fail to acknowledge their sources correctly -- either intentionally or inadvertently -- commit plagiarism. And writers who unfairly use copyrighted material found on the World Wide Web or in print are legally liable for their acts.