With increasing availability of so many types of information and sources online, the rules for appropriate citation of sources may be less clear than in the old days of paper.  Here are some guidelines regarding two important questions:
- WHEN do I need to cite sources?
- HOW do I cite sources?

I. WHEN to cite:

This is one of the most important questions in scholarly work; failing to cite appropriately can be one of the most serious scholarly sins (and can seriously affect your evaluation).  There may be some gray areas around the edges, but the underlying principles are straightforward:
Failure to adhere to these principles appropriately constitutes plagiarism and will affect your evaluation; egregious or repeated plagiarism may result in failure of the class.  There must, obviously, be a threshold for these standards; you do not need, generally, to cite a supporting reference for statements of 'common knowledge' (e.g., that the earth is round -- unless, say, you were analyzing the history of this understanding, or some particular claim about it; then cite!). You do not need to cite a short, common phrase (like 'common knowledge') as a quotation, even though someone must have used it first...  You must use your (informed) judgment.  But, if you're unsure, ask -- or go ahead and cite source!

II. HOW to cite:

The basic principle here is straightforward.  Your citation of a source should allow your reader to locate that source easily.  However, the particulars of format, what information should be provided, etc. are trickier than they used to be when cited work was almost always published on paper.  SO, here are some guidelines.
  1. REFERING TO A SOURCE in your writing:  There are lots of varying standards here, even within the world of scholarly work.  Some use footnotes, some use endnotes, some insert author and date in text with a 'references cited' section at the end, etc. I ask you to choose a standard and use it consistently.   The easiest approach, if this is new to you,  might be to look at a scholarly publication (we'll be reading a variety of them), and imitate its style.
  2. INFORMATION TO INCLUDED IN A CITATION: As noted above, your full citation (either in first foot/end-note to a source, or in list at end of paper) should include essential information for locating the citation.  That will differ, however, depending on nature of source:
  3. Note that a 'references cited' list is not necessarily the same as a 'bibliography'.  The latter may include sources pertinent to your writing even if you don't make explicit and direct use of them.  You must give full references for things you cite; a bibliography is an option (unless specifically requested).
  4. It's fine to incorporate hyperlinks directly in on-line material (like wiki articles) produced for class, but you should still provide explicit citation info as discussed here.
Here are a few examples of full citations for different types of sources and in different formats -- all acceptable -- just to give you a sense:

Dockrill, S. J., and J. M. Bond. 2009. Sustainability and Resilience in Prehistoric North Atlantic Britain: The Importance of a Mixed Paleoeconomic System. Journal of the North Atlantic 2:33–50. doi: 10.3721/037.002.0105.

Crosby, A. W. Germs, Seeds & Animals: Studies in Ecological History. ME Sharpe Inc, 1994.

Wright, Karen. 1998. “Empires in the Dust.” Discover (March): 94–99.

Anon. Atlas of the Biosphere. 2010. Available at: Accessed September 18, 2010.

“Progressive Forest Clearing, Bolivia.” Text.Article, December 22, 2008.

III. Managing bibliographic and citation information.

While you don't have to do this to meet expectations listed above, I'd recommend that you think about using some available tools for managing your reference/bibliographic resources.  I use a very powerful and intuitive and FREE reference management package called ZOTERO.   Zotero is open-source, and  is very good at both 'capturing' reference information from on-line material and at generating in-text citations and references cited lists and bibliographies.  You can also use it to store materials (including full pdf's of source) in the cloud and synchronize your database across machines.

-- KW, Feb 2013