16 steps to the 16th edition
Step 13. E-mail {CMS rule 14.222 and 15.48}
CMS 16 dictates that citations to e-mail should used only in running text and notes, and are therefore not listed in a Bibliography or a Reference List, or cited parenthetically. An e-mail address belonging to an individual should be omitted. If used, it must be cited by permission of its owner. The term personal communication (or pers. comm.), may be used after the name(s) of the person(s) concerned, following a comma. As noted, reference list entries are unneeded, though each person cited must be fully identified in the text. In whatever form interviews or personal communications (pers. comm.) exist—published, broadcast, preserved in audiovisual form, available online—the citation normally begins with the name of the person interviewed or the person from whom the communication was received. The interviewer or recipient, if mentioned, comes second {CMS 14.218}.
Step 14. Online multimedia {CMS rule 14.280 and 14.274 }
Documentation of a recording usually includes some or all of the following pieces of information: the name of the composer, writer, performer, or other person primarily responsible for the content; the title, in italics or quotation marks, as applicable; the name of the recording company or publisher; any identifying number of the recording; indication of medium (compact disc, audiocassette, audiovisual file, etc.); and the copyright date or date of production or performance. Recordings (audio casts, pod casts, video casts…) consulted online should include a URL or DOI. Either of these elements has the potential to lead readers directly to the source cited, and researchers are encouraged to record them as part of their source citations. Online multimedia must be cited with a date.
Step 15. Electronic articles {CMS rule 14.184 }
When citing electronic articles, a DOI, if available, is preferable to a URL. If using a URL, use the address that appears in the address bar, unless a shorter, more stable form of the URL is offered. Note that a single DOI assigned to a journal article as a whole applies to that article in any medium, print or electronic. (Because the DOI points to all available formats simultaneously, it is not necessary to specify which electronic format was cited—e.g., PDF or HTML.). Dates should immediately precede the DOI or URL, separated from the surrounding citation by commas in a note and periods in a bibliography entry. This departure from Chicago’s earlier recommendation recognizes the increasing importance of uniform placement of URLs and DOIs in source citations {CMS rule 14.185}. In certain cases, when citing an article consulted online, it may be advisable to shorten a particularly unwieldy URL to end after the first single forward slash; i.e., the slash that follows a domain extension such as .com {CMS rule 14.203}.
Step 16. Ibid. {CMS rule 14.29}
If you cite the same source and page number(s) from a single source two or more times consecutively, the corresponding note should use the word “Ibid.,” an abbreviated form of the Latin “ibidem,” which means “in the same place.” If you use the same source but a different page number, the corresponding note should use “Ibid.” followed by a comma and the new page number(s). The abbreviation ibid. usually refers to a single work cited in the note immediately preceding. Ibid. is used in place of the author's name, the title, and as much of the information as is identical to the immediately preceding note. It cannot be used if the preceding note cites more than one work. Ibid. is not used in a bibliography or a reference list; to represent the same author or editor named in the preceding entry use the 3-em dash {CMS rule 6.91}.
The full text of the Chicago Manual of Style is available online at http://www.chicagomanualofstyle.org/home.html