Thanks. I think the .pdf that links from Google is in fact from an online journal - I may see if it's still there and then I can provide the URL. Another similar example I have, however, does not exist except in a "cache" from Google scholar, so I guess then, that's what I'll need to cite. The style guide from the journal that sponsors the conference is MLA, which I'm familiar with but tends to be a bit on the side of over- rather than under - citing.