And, it's as easy as pie to use... just put in something that relates to the thing you want to create a reference for... many identifiers work...
- Pubmed - all you need is a Pubmed ID (PMID), a DOI or a unique search. Only the first result will be returned.
- ISBN search - a formatted book citation (you can use ISBN-10 or ISBN-13, but it'll need to be valid
- URL - the url of the publication (including a pdf)
- Books - an amazon or google books URL
- Other commonly cited websites, e.g. eMedicine, whonamedit