Sometimes information is taken from a database, such as in the case of UpToDate, or MedlinePlus. You are still required to cite the source from which you obtained the information. For example:
1. Doelken, P. 2012. Placement and management of thoracostomy tubes. UpToDate. Topic 7816 Version 12.0. Available: http://0-www.uptodate.com.innopac.wits.ac.za/contents/placement-and-management-of-thoracostomy-tubes?source=search_result&search=traumatic+pneumothorax&selectedTitle=2~150 [Accessed 16.01.2013]
Note in the example above that UptoDate provides a Topic number and a version number at the end of the text. It is useful to cite this information after the name of the database.
2. Body weight. 2012. MedlinePlus Available: http://www.nlm.nih.gov/medlineplus/bodyweight.html [Accessed 16.01.2013]
Note in the second example above that at the bottom of the web page there are two different dates: one is the date on which the page was updated; the other is the date the content was last reviewed. Use the date when the content was last reviewed.