There is also a web site (USIN.org), complete with examples and source code. Identifiers for books are straightforward, for instance bibp:ISBN/0-86542-889-1 identifies a certain book:
For journals things are slightly more complicated. However, Cameron simplified things a little in his subsequent paper Scholar-Friendly DOI Suffixes with JACC: Journal Article Citation Convention (also on Scribd).
JACC (Journal Article Citation Convention) is proposed as an alternative to SICI (Serial Item and Contribution Identifier) as a convention for specifying journal articles in DOI (Digital Object Identifier) suffixes. JACC is intended to provide a very simple tool for scholars to easily create Web links to DOIs and to also support interoperability between legacy article citation systems and DOI-based services. The simplicity of JACC in comparison to SICI should be a boon both to the scholar and to the implementor of DOI responders.
USIN and JACC use the minimal number of elements in order to identifier an article, such as journal code (e.g., ISSN or an accepted acronym), volume number, and starting page. Using ISSNs ensures globally unique identifiers for journals, but the scheme can also use acronyms, hence those journals that lack ISSNs could be catered for. The scheme is simple, and in many cases will provide the bare minimum of information necessary to locate an item via an OpenURL resolver. Indeed, one simple way to implement USIN identifiers would be to have a service that takes URIs of the form <journal-code>:<volume>@<page> and resolves them behind the scenes using OpenURL. Hence we get simple identifiers that are resolvable, without the baroque approach of SICIs.
When I get the chance I may add support for something like this to bioGUID.