There are a number of standard methods for quoting, or citing, references correctly.
Different subjects require the use of different methods.
If you are writing a scientific article, the periodical which you hope to publish it in will tell you which system it prefers, in the Instructions to Authors section. The method most commonly used for Biological Sciences is described here. The following system should be used by undergraduate students to cite references in essays and projects. In the text of an essay or project, whenever a piece of information is included which is derived from another source, such as a textbook or periodical article, you must say where the information came from. You should not give the full details of the source within your text, but in a reference list, or bibliography , at the end.