I have collected some papers regarding the subject of my M.A. thesis, but I have some articles that I couldn't find where they were published. The point is when I Google the title of the article, Google shows me that the article has been cited more than 60 times, but I can't find where and in what journal. How can I find the journal in which these articles were published?
Google Scholar typically offers "Cite" button that will give you its best bibliographic information available on the citation. That will usually give you everything you need. If not, follow the links in Scholar to where it found the article, and there will usually be bibliographic information. And you can also do as @aeismail suggests and look at how others have cited it.
For some particularly odd or obscure articles, however, you may still be unable to find an appropriate set of journal/conference information. For example, technical manuals often have no official publication, but just an online reference site that is being maintained. Another example is the Carlson Curve is widely referenced but has no official publication beyond a series of blog posts. Still, there is always a correct way to cite: follow the principle of giving the most complete and persistent data that will allow others to find the same information that you found.