In some senses, the internet seems a great melting pot for news, with so many sites linking to stories from other sites, or rewriting stories from elsewhere with a link to the original, or simply lifting stories whole, that one might think the whole issue of copyright is a thing of the past, of the printed era.

But in fact more and more publishers are growing irate over seeing their work appropriated by others without permission, and the latest to join that protest is the Associated Press, the cooperative news agency that for so many years was a primary source of news for newspapers, radio and television, and more recently for the internet.

On Monday the news agency said it would begin cracking down on sites that picked up its stories without a license, suing where necessary to stop the practice.

It also intends to seek a share of revenue from sites, such as news aggregators, that put up links to stories appearing elsewhere. The aim is not to halt the dissemination of news stories across the internet but to gain tighter control over how AP stories are used and credited.

The issue is what's in legal terms known as fair use. One publisher may quote from work that appears elsewhere provided that secondary source is given proper credit and where the material quoted is limited, such that the bulk of the new article is original and could stand on its own were the quoted matter not included.

So a sentence or a paragraph quote from another article might be considered fair use but several paragraphs or a page would be considered an abuse of fair use.

What makes the fair use issue so murky on the internet is the manner in which many stories are linked. Preceding the link might be a one-sentence introduction, which has become quite common among news aggregators like Yahoo. But more and more sites are rewriting or capitalizing stories, then offering the reader a link to the original. Publishers argue that's an abuse of fair use.

But is it? Legal authorities note that it's a gray area, with no definitive court rulings publishers can turn to.

But the bigger issue for the AP as its member newspapers struggle with declining profits and circulations is that the major search engines like Google and Yahoo profit by linking stories that first appeared on AP member sites without sharing revenues from the search advertising that appear on those pages, though they may pay fees for use of that content.

Just how the AP plans to go about gaining a share of those revenues is unclear, and the news agency is offering no specifics, but presumably it intends to negotiate new terms by which aggregators can link stories from member news organizations.