If you can not find some of the information needed, cite what is available.The following Works Cited/Bibliography examples are only guidelines; utilize the MLA Handbook for Writers of Research Papers for additional examples.Note that Bibtex has a special field for url, but you can also add it as a note. For academic publications, there is an OPTIONAL URL field you may use, but this should be in addition to citing the original conference/journal/workshop/etc.
For example, I used a URL resource from the libary of congress because it was unpublished historical (circa 1890AD) blueprints scanned into their library.
give the more traditional reference information as well.
What you need (at minimum): Because URL are (usually) not eternal, but hopefully your publication is, then I wouldn't advise to only put an URL, especially for books or paper.
It doesn't add much to make a full biblio item, that can of course include the URL! For example if you are citing books.google.* , then you need to cite that book as a book and not a URL.
The URL could change at any given time without notice.
Author Research Paper Example
Also, you are assuming that everyone is reading your paper electronically and has access to the internet.
Or is it compulsory to give proper authors, title, year of publication, etc... Example: Data mining is the process of analyzing large data sets in order to discover hidden patterns within these data sets. Stock market prices do not follow random walk. 
id=5FIEAwyn9ao C  No, it's not OK to cite URLs because firstly, you are citing ONLY the URL!
Second, physical references are equally transient, if in a different way...
usually that many different libraries throughout the world maintain "cached" copies.