Should citations on PowerPoint slides be shortened? Are there guidelines or best practices for adding references to a research PowerPoint presentation?

For example, should I put the full citation at the bottom of the slide?


  Liu, J., Rinzler, A. G., Dai, H., Hafner, J. H., Bradley, R. K., Boul, P. J., Smalley, R. E. (1998). Fullerene Pipes. Science, 280(5367), 1253–1256. 


If you have even a couple references, this slide starts to look really busy. 

I've seen quite a few presentations with truncated references (just first author, journal, year), like so:


  Liu, J., et al. Science (1998)


Is this shortened reference alright? It looks cleaner on the slide, but at the expense of the ease of the viewer locating a reference. Any other solutions? If it makes a difference, this would be for the engineering/science fields.
I would strongly recommend against putting the full citation at the bottom of the slide.  The problem is, when you are actually presenting, it will both a) make the slide look very busy as you note, and b) distract people away from the rest of the slide.  Another problem is that few people will actually be able to copy down the citation (unless you linger on the slide for a very long time).

Truncated references deal with all of these problems, generally giving just enough information for a quickly scribbled note that will give the reader the ability to track down the cited paper with a little bit of work.

In addition, however, if you will be making the slides available for others to read at their leisure, there are two other good places to put references:


A "bibliography" slide at the end, before or after where many put the funding/acknowledgements slide.
In the "notes" field associated with the slide on which the truncated reference appears.


This is especially good when dealing with funding agencies, who like to pull slides out of your deck for presentation to their own higher-ups.