How can you find the DOI of an article that doesn't seem to have one? I cannot find the DOI number of this article. It has ISBN, but it does not help me find its DOI number.

How can you find the DOI number of articles where it's not listed, but other identifiers, such as an ISBN, are available?
Try these sites to search for a CrossRef DOI:

http://search.crossref.org/

or

http://www.crossref.org/guestquery/