Citing your sources means you cite the resources you used for your writing so as to give credit to those people whose idears or words you are using in your paper and to distinguish their ideas/words from your own. It also allows your readers to verify your claims and to get more information from the source materials.
For more guidance, please review Citing Your Sources Guide.
Here are some printed information:
Chicago Manual of Style (CMOS)
REF DESK Z253 .U69 2003
MLA handbook for Writers of Research Papers (MLA)
REF DESK LB2369 .G53 2003
Manual for Writers of Term papers, Theses, and Dissertations (Turabian)
REF DESK LB2369 .T8 1996