Referencing articles you've used is important - it demonstrates that you've researched your topic, it allows others to find the article to read for themselves, and it avoids accusations of plagairism.
Check out our Citing and Referencing page for more information.
A correctly formatted reference will tell you exactly where to find the full article:
DING, Y., JACOB, E. K., ZHIXIONG, Z., FOO, S., ERJIA, Y., GEORGE, N. L. and LIJIANG, G. (2009) Perspectives on social tagging, Journal of the American Society for Information Science and Technology, 60 (12), 2388-2401.
This article was written by Y Ding & colleagues, and the article's title is "Perspectives on social tagging". It was published in 2009 in the journal called "Journal of the American Society for Information Science and Technology". It was published in volume 60, issue 12, and the article ran from page 2388 to 2401.
If you're looking for journal articles, these are some of the key databases you'll need. You can see some other useful databases below, and the listing of Science and Engineering Datasets.