The new Citation Tracker feature allows searchers to review citation counts for a particular author's works and to present a Citation Overview table broken down by individual years and brief article titles for the years the user has designated in a date range field. Users can also search a subject field for a list of articles, select the ones of greatest interest, create a temporary list, and then create a citation overview for the articles on the list. Permanent saving of the list enables calling the citations up for future reviews. Links from the tabular data in the overviews will display the full citations for the citing documents. A refine box allows users to set certain limits as to document type (e.g., review versus article), category (e.g., engineering, chemistry, geology, etc.), and so on, and to read a summary of key factors, e.g., most-to-least citing authors, journals, etc. (For a demonstration of Scopus Citation Tracker, go to http://www.info.scopus.com/ctracker.)

The issue of content coverage underlies any evaluation of a citation searching service. Of its 14,200 journal titles, 4,500 come from chemistry, physics, mathematics, and engineering; 5,900 are from life and health sciences (including 100 percent overlap with Medline); 2,500 come from biological, agricultural, and environmental sciences; 50 are from general science; and 2,700 come from social sciences, psychology, business management, and economics. However, according to Amanda Spiteri, director of marketing for Elsevier, Scopus indexes all the same source journals as Thomson ISI—excluding Arts and Humanities—plus more. The service also handles 750 conference proceedings and 400 trade publications. Beyond its 531 OA journals, Scopus has an integrated interface with Elsevier's Scirus Web search engine, which accesses more than 200 million science-specific Web pages, including preprint servers, Open Archive Initiative (OAI) sources, and patents—e.g., Cogprints, ArXiv.org, and USPTO.

Spiteri conceded that Thomson has many more decades of coverage than Scopus. For example, coverage in the social sciences only goes back to 1996. However, she said that their research had indicated that more than 80 percent of user needs were met by more current material. "It's not 100 percent, but it is the optimum." She also pointed out that Citation Tracker offers "real-time" citation searching. "Whenever a searcher runs a citation analysis, the system calculates from fresh data, not static. The service is updated daily." However, Scopus dates its references and citation searching from the date of publication (usually print date), rather than any appearance in a Web-based cite. It should be interesting to observe if it hews to this policy now that Elsevier Science Direct has launched an "Accepted Manuscripts" service that supplies peer-reviewed, finished manuscripts on the Web site that are still in the pipeline for print publication. Commenting on the general problem of "versioning" in a world of open access, institutional repositories, preprint servers, etc., Spiteri said it was a problem for the whole industry. Jim Pringle, vice president of product development at Thomson Scientific, echoed her sentiments.

Though the promotional materials for the Citation Tracker service claim that it enables users to "quickly identify research trends to see what's hot and what's not," the service does not have the ability to scan research flow and identify top areas of research. If searchers can designate a "hot" field, it looks like Citation Tracker can tell them "who's hot" in that field, i.e., which authors and affiliated institutions and journals cover a stimulating area of research. Spiteri admitted: "We are not doing broad bibliometric scanning to break down a field; it is not designed for that. Instead it's for an individual who knows [his or her] field, like [a] post-graduate or post-doctorate [level] of researcher. We are talking to some bibliometric organizations for the potential of going forward." For information products built out of expert bibliometric analysis, users would probably do better to look at Thomson ISI's Web of Science. However, one user with whom I spoke thought that the Citation Tracker in Scopus would solve many users' needs, particularly with its friendlier user interface.

Elsevier began developing Scopus in 2002 with extensive user testing at 21 institutions and with more than 300 researchers worldwide, before launching in November 2004. According to Spiteri, Scopus now has more than 1,000 subscribers, 300 of whom are on 3-year contracts. The company continues to extensively test new features under development with user groups. Future developments for Citation Tracker should include the ability to exclude self-citations, which is important for those buttressing tenure claims; changing sorting order; deleting records from a citation overview; and linking to record pages.