Yahoo has begun a fee-based premium search feature that will provide customers with access to reference reports, news and authoritative content.

The company will offer the Premium Document Search service for users to search a library of more than 70 million pages of full text from more than 7,100 newspapers, trade journals and other sources.

Consumers can also purchase reference reports and access archived news from more than 60 US and international newswires.

The search engine will charge $4.95 a month for 50 documents, or a per article fee of between $1 and $4 to retrieve files.

Yahoo will make the service available through an agreement with enterprise service provider Divine, which recently purchased search and content assets from Northern Light Technology.

Scott Gatz, vice president, search and directory at Yahoo, said the agreement builds on the company's business strategy to exploit the core strength of its leading search and directory service.

"The Divine Special Collection library is a great fit for our global online audience," he explained. "This fits into the company's desire to diversify revenue and more effectively 'monetise' search and directory."

Yahoo also said it will offer a free document summary before purchase and a money back guarantee.

Meanwhile, Yahoo's traditional search engine, provided by Google, and its in-house directories, will remain free.

The company announced an agreement last November with paid search facility Overture Services to integrate pay-for-placement listings into its search results. The service allows advertisers to bid for placement in query results rather than rely on natural listings or editorial recommendations.

Yahoo, which has been relying more on fee-based services after its advertising sales plunged last year, has also begun to charge visitors for services such as more email memory, real-time stock quotes and auctions.

In addition, Yahoo agreed to buy HotJobs.com last year as part of its strategy to generate revenue from non-advertising initiatives.