Beginning in 2005, SPIE journals transitioned from traditional page numbers to six-digit citation identifiers (CIDs). Use of CIDs in place of traditional page numbers allows an issue to build online one article at a time, while retaining the ability to segment tables of contents by article type or subject area. This accelerates online publication of individual articles, which are published online individually as soon as author proof corrections are incorporated. Utilization of CIDs also allows articles to be fully citable as soon as they are published online, using the same identifier for both online and print versions.
The structure of the six-digit CID is defined as follows:
- First two digits (01-12) indicate the issue number, or in the case of single-volume annual journals, the volume number
- Middle two digits (01-99) indicate the article type and/or subject area
- Last two digits (01-99) are assigned according to publication order, within that issue and section
Current article types and subject areas (the middle two digits of the CID) vary by journal.
The format for citing articles published in SPIE journals uses the six-digit CID in the place traditionally filled by a page number. An example of the correct citation format for an Optical Engineering article is:
A. Smith and B. Jones, "Paper title," Opt. Eng. 44(2), 023407 (2005).
In this fictitious example, the article by Smith and Jones was published in Optical Engineering in Issue 2 of Volume 44, as the seventh article published under section category 34.
In the full-text PDF file available online and in the printed article, the CID appears on each printed page. Appended at the end of the CID is a hyphen followed by a consecutive page number. For the sample article above, the printed pages would carry this page numbering: 023407-1, 023407-2, 023407-3, etc. The hyphen and additional digits should not be used when citing or searching for an article.
Direct questions and comments about CIDs to the Office of the Managing Editor at email@example.com.