NEW YORK (AP) _ Programs such as ``Frontline'' and ``Nova'' and historical programming that included a look at the Bay of Pigs invasion, helped PBS top this year's Emmy nominations for news and documentary awards.

The publicly funded network received 27 nominations, followed by CBS with 24, NBC with 21 and ABC with 20.

Coverage of the Princess Diana tragedy generated the most selections for CBS, NBC and ABC in the breaking news categories. Flooding in Grand Forks, N.D., was the second-most nominated story of the year.

``The large number of entries . . . reflect broadcasters' continuing emphasis on news and documentary programming,'' said John Cannon, president of the National Academy of Television Arts and Sciences.

PBS swept through the categories of historical programming and individual achievement for the work of writers, engineers, music editors and lighting and graphic designers.

``CBS Evening News'' and ``60 Minutes'' gave CBS the most nominations in the news categories.

Other cable networks with nominations included Discovery with 11, TBS with seven, TLC with six and Cinemax and CNN with four each.

Awards will be presented Sept. 8 in New York.