Frequently Asked Questions about the APS link manager

• What is the APS link manager?
• How does one link to a specific APS journal homepage?
• How does one link to a specific APS journal article?
• How do I link to an article that uses a six digit identifier in lieu of a page number?
• What about DOI's and CrossRef?
• What functionality does the link manager have?
• How long will the links be maintained?
• What APS offerings are currently online?
• Why link to the abstract and not the article (PDF)?
• How does the link manager handle non-unique citations?
• What algorithm can one use to generate correct URL's for APS citations?

What is the APS link manager?

The APS link manager facilitates linking to our online journals by providing a very simple URL scheme based only upon the information found in a typical journal citation. In particular, issue numbers are not needed even though some of our online offerings use URL's that require the issue number. The APS has promulgated a policy of keeping all abstracts in our online offerings freely available, making them a natural target for outside links into our journals. By using the APS link manager, researchers, publishers, and libraries can link easily to Physical Review without worrying about future changes in the location of our online services, changes in the URL's that are used internally for these services, or broken links because of subscription limitations.

Currently the link manager only supports linking to the abstract/wrapper, but support for linking to tables of contents, the PDF articles, and other deliverables may be added (but see below). The idea of the link manager is to insulate outside users from potential future changes in the location of our online services or in the URL's that are used internally in the online offerings.

How does one link to a specific APS journal homepage?

Each journal has its own homepage with a very simple URL:

How does one link to a specific APS journal article?

The overwhelming majority of cases can be handled with a very simple URL. For instance, to link to Phys. Rev. D 55, 1 (1997) one can use the following URL:

link.aps.org/abstract/PRD/v55/p1

(N.B. The server publish.aps.org still works (and will always work), but link.aps.org is preferred now.)

• The journals are abbreviated PRA, PRB, PRC, PRD, PRE, PRL, PRSTPER, PRSTAB, PR, PRI, and RMP. PR is for Physical Review Series II (1913-1969) and PRI is for Physical Review Series I (1893-1912).
• Case doesn't matter for the "fields" of the URL that follow the /abstract/ keyword.
• The order of the fields (after /abstract/) doesn't matter.
• If the article is a Rapid, the 'R' may either be included in the page number or left out (as in the above case which is really a Rapid).
• Leading zeroes in numbers are ignored, except for our new six digit electronic identifiers (the link manager will tolerate omitted leading zeroes in electronic identifiers).

In addition to the fields above, there are other fields available which may be put into the URL. These fields are optional and will be used eventually to provide some error checking. Again, these fields may appear in any order and are case insensitive.

• /y..../: A four digit year.
• /i..../: The issue number (any number of digits).
• /e..../: Electronic identifier - replaces page number for recent issues of all Phys. Rev. journals
• /s..../: Sequence number (any number of digits). This is for the case when there are multiple items that start on the same page so that the journal/volume/page citation isn't unique. This often occurs for errata, comments, and replies to comments. See below.

How do I link to an article that uses a six digit identifier in lieu of a page number?

Some of our journals now use six digit article identifiers in lieu of page numbers. The table below summarizes which journals currently use them.

All Phys. Rev. journals now use this system. An example citation is Phys. Rev. D 58, 013001 (1998). Articles cited this way should use the /e..../ field instead of the /p..../ field. The URL for this example would be link.aps.org/abstract/PRD/v58/e013001. The link manager will tolerate using the /p..../ field for electronic identifiers, but this is deprecated.

What about DOI's and CrossRef?

APS is a member of CrossRef, an organization formed by publishers to facilitate linking to journal articles. APS has registered DOI's for our articles (or is in the process of doing so). APS DOI's are constructed in much the same way as our link manager URLs, so it isn't necessary to use CrossRef to obtain our DOIs (APS has also implemented a query interface similar to CrossRef's which can be used to check DOIs without charge. Interested parties should send e-mail to doyle@aps.org).

The APS DOI prefix is 10.1103. The DOI suffix consists of a journal abbreviation, the volume, and the page number or articled id separated by dots (.). The journal abbreviations are:

Thus the DOI for Phys. Rev. D 58, 013001 (1998) would be 10.1103/PhysRevD.58.013001 When an article has a sequence number higher than 1 (that is, when more than one article starts on the same page, the first article has sequence number 1, the second 2, etc.), the sequence number is appended with a dot separator to the rest of the DOI. This usually only happens for errata and replies to comments.

A DOI can be turned into a URL by appending it to dx.doi.org/: dx.doi.org/10.1103/PhysRevD.58.013001

What functionality does the link manager have?

The link manager includes the following functionality:

• Checks if the URL contains the minimally required journal/volume/page (or electronic identifier) information.
• Checks if the citation is valid.
• Checks if the citation is online.
• Redirects the browser using the "Location:" directive to the proper URL.
• Tries to give informative error messages.

How long will the links be maintained?

The intention of the APS is to maintain these URL's for as long as necessary, which basically means until URL's are no longer widely used as a means of locating content on the World Wide Web. As our online offerings evolve, these URL's will continue to point to something appropriate.

What APS offerings are currently online?

We now have online all Physical Review and Reviews of Modern Physics content back to their start as part of our Physical Review Online Archive (PROLA) project. The following table summarizes what we have online:

Why link to the abstract and not the article (PDF)?

Currently one can only easily link to the abstracts, so the point is moot. But even if the PDF files were directly available through the link manager, the APS would strongly urge linking to the APS abstract page. At worst, if one were to link to the PDF files or other deliverables, one should also include a link to the abstract page as well. There are several reasons for this:

• The APS has made the abstracts available to everyone free of charge. Thus links to the abstract page will work for anyone, even non-subscribers. PDF files and other deliverables are not freely available, but require a subscription.
• The user will be able to see the size of the file they are about to download before they actually start the download.
• There are other deliverables besides PDF. We offer PostScript now and we hope to offer SGML in the future. Furthermore, some formats may be delivered in multiple ways. For instance, we are planning to make PostScript available compressed with a variety of different schemes. Users should be given the choice of downloading the format that they want.
• The user may decide that they need to browse or search the journal further. By following a link to the abstract page, the user (subscriber) has full access to the rest of the features of the journal (including links to related articles like errata and comments and to referenced articles).
• There will always be an abstract wrapper page, but at some future date, a particular deliverable may become obsolete. By linking to the abstract page, you leave the burden of maintaining links to the various deliverables to the APS.

How does the link manager handle non-unique citations?

Non-unique journal/volume/page citations are possible with APS journals because we sometimes publish multiple errata or comments on a single page. If one knows the position on the page of a particular item, then one can use the "sequence" number field (/s..../) to indicate which item one is interested in. However, it is often the case that a citation to one of these errata or comments won't indicate a sequence number. In this case, the sequence number can be omitted and the user will be presented with a list of URL's for each item on that particular page.

What algorithm can one use to generate correct URL's for APS citations?

The link manager is designed to be rather forgiving in how people construct URL's to link to the journals. However, because we are introducing electronic identifiers for some journals in lieu of page numbers and because the identifiers and page numbers superficially resemble each other, it may be helpful to have an example algorithm to generate the proper URL's. Here is a simple outline of the current algorithm (as of July 2001).

1. Determine if the article is online (see table above).
2. If journal is e-first (such as Phys. Rev. D and volume is greater than 57, or journal is Phys. Rev. ST Accel. Beams), interpret "page number" as electronic identifier.
3. Generate URL from journal name, volume, and either page number or electronic identifier.

If you have any questions or comments please send email to help@aps.org.