WHITAKERWEB GREEN SERVICE Whitaker (+44 171 420 6000) Annual subscription Pounds 1,285 (monthly);Pounds 905 (bimonthly); single disc Pounds 475 (+VAT) ISSN 1361 3553 Windows CD

Whitaker Bibliographic Services claims to hold the most comprehensive bibliographic file of English language books and audio books; the total file contains nearly two million titles, and apparently each month more than 80,000 amendments are made to it.

The records are available in print, microfiche and CD-Rom. New this year is a CD-Rom version with a Windows interface.

Buying the monthly updated CD-Rom of the Green Service (UK and English language titles in print, recently out of print and forthcoming) costs more than five times the price of the annual print version; justifying that kind of expenditure is difficult.

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The advantages of a CD-Rom over a book (apart from the saving on shelf space) are the comprehensiveness and currency of the information provided, and the facility to manipulate and download data, which a computer can do speedily and with effortless simplicity. Or, rather, it should be able to; the first disc I tried turned out to be faulty, a fact only discovered after several frustrating attempts to load it on two different PCs.

The technical support person was polite but her advice misleading, and after spending some time trying to install it I found that the "unlimited technical assistance" offered only operates during weekday office hours.

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Since most of Whitaker's customers are bookshops and public libraries, this seems a serious drawback.

However, a replacement disc arrived and installed like a dream. The manual accompanying it is excellent; clearly laid out and generously sized, it explains the various functions in a straightforward way that instils confidence in both the system and your ability to navigate it. Searching the database can be performed on three levels. The simple "query by form" option pulls up a screen in which author, title and other details are filled in. The more advanced "structured" and "expert" levels cater for those with experience of Boolean logic and keywords, and are suitable for doing complex searches across various fields.

A search for a particular title will display on screen all the details needed to order books, including publisher, price, ISBN and availabilty from wholesalers and library suppliers.

General searches can be made using Whitaker's own subject headings (there are only 150 of these, which is hardly comprehensive in scope) or Dewey numbers, and results can be filtered by such criteria as date of publication or price.

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The correct form of names or titles can be checked by using the "browse" facility, and truncation and wildcard searching is also possible if you know some, but not all, of the letters in a word. There is also a separate database giving addresses, phone and fax numbers of thousands of publishers; but be warned, entering it will lose your existing searches unless you save them first.

Data can be customised, manipulated and downloaded into word processing packages, to create basic catalogue records, for example. TeleOrdering is a possibility for customers who subscribe to the wider package of services Whitaker offers; this means books can be ordered and paid for electronically.

Generally, it is a very easy system to master. There are plenty of help screens if you do not want to refer to the manual, and if you need it Whitaker offers, at extra cost, customised training for small groups. I was impressed by the amount of bibliographic information the disc holds, and its accessibility; the only drawback is the price.

With the recent launch of the broadly similar Bookscope CD-Rom from Primary Source Media, which includes reviews of books and is much cheaper, it may be that the increased competition will eventually bring prices down. There are now a number of bibliographic databases available, and customers should choose carefully before parting with the considerable sums of money involved in subscribing to one of them.

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Elaine Saunders is a librarian at Times Supplements Ltd.