Documentation Systems: An Overview
How Sources are Documented
Conventions for documenting source material differ slightly from style to style; however, both in-text citation and end documentation are universal requirements.
They are used in conjunction with each other: First, the in-text citation flags the reader's attention identifying the source material and second, the end documentation catalogues the bibliographic information flagged by the in-text citation.
Note: The Chicago Manual of Style points out an exception: when only a handful of sources are used, footnotes may replace end documentation.