It is important that you correctly reference the sources you have quoted, paraphrased or summarised in your work. You must acknowledge all the sources you use in a process called ‘referencing’.
Depending on the referencing style you use, external sources are usually listed twice:
1) in the body of your work in the form of in-text referencing
2) at the end of your work in the form of a compiled reference list.
Remember to check with your department to find out exactly which referencing system they prefer.