When citing a journal article using footnotes in the humanities (where of course particular journal styles will vary but in general Chicago Manual of Style is used), the proper format is to give the full citation the first time it is cited. However, after the article is cited for the first time, a shorter version is used for all subsequent times (involving only the author's last name, the omission of the journal, etc.). One of the ways these subsequent citations are shortened is by not including the full title of the article. I have seen many variations on how this should be done (where some seem intuitive, others less so).
Is there an actual acceptable standard for choosing the short title? If not, how should one go about choosing an appropriate short title?
An example: This article by Ole Benedictow, "What Disease was Plague? On the Controversy over the Microbiological Identity of Plague Epidemics of the Past" would be reasonably shortened to simply "What Disease was Plague?"
Another note: This convention of shortening citations is also used for books and other materials, but I ask about articles because choosing a short title is more often less intuitive.