April 28, 1986

International President Reagan rejected a claim by Ferdinand E. Marcos that he is still the rightful President of the Philippines, White House officials said. Mr. Reagan spoke by telephone to Mr. Marcos soon after Mr. Reagan arrived in Honolulu on the second day of his 13-day trip to the Far East for a meeting with foreign ministers of Southeast Asian countries in Indonesia and to attend the annual ecnomic summit meeting in Tokyo May 4 to 6. The phone conversation was the first direct contact between Mr. Reagan and Mr. Marcos since the deposed President fled the Philippines Feb. 26. White House officials said Mr. Marcos's claim to the presidency was turned down gently, but firmly. [ Page A1, Column 6. ] Ferdinand E. Marcos told followers that he was ''ready to fight'' and that they should keep demonstrating in his behalf without violence. The deposed President spoke by telephone from his house in Hawaii to a rally in Manila attended by 10,000 people. The call lasted nearly 20 minutes. Mr. Marcos did not refer to the telephone call that he received earlier from President Reagan. [ A11:1. ]

A music review on Thursday about the Greitzer Ensemble at Merkin Concert Hall misstated the family connection of the flutist Jody Schwarz. She is a daughter of Sol Greitzer, the violist and conductor, and Shirley Greitzer, the pianist.

Three of the world's top 20 advertising agencies are combining in a first-of-its-kind merger to create, for the time being at any rate, the largest such company. BBDO International, the Doyle Dane Bernbach Group and Needham Harper Worldwide signed the merger agreement Friday night. Yesterday they announced their plans for a holding company to handle about $5 billion a year in advertising billings. ''We want to be nothing less than advertising's global creative superpower,'' said Allen G. Rosenshine, chairman and chief executive officer of BBDO. His agency created the Pepsi-Cola advertising that won every top prize in last year's major ad competitions. For advertising clients who need extra creative resources, Mr. Rosenshine said, the new set-up will give them the option of avoiding a lengthy search for a new agency.

A year ago in Atlanta, presiding over his first annual meeting as chief executive of the International Business Machines Corporation, a confident John F. Akers predicted that his company would post ''solid growth'' in 1985. Within two months he backtracked as a stubborn computer slump began to drive I.B.M. to its first yearly profit decline in six years. This morning in Houston, a still-confident but more cautious Mr. Akers goes before I.B.M.'s shareholders for a second time, and if he has any predictions for the year, he is planning to keep them to himself. ''I'll just smile,'' he said, shrugging his shoulders during a recent interview at the company's Armonk, N.Y., headquarters, ''and say, 'We'll just see how things turn out.' '' By I.B.M.'s standards, things have not turned out too well for nearly a year now, so the 50-year-old Mr. Akers may face some tough questioning from the floor this morning.

The recent spate of terrorist attacks against Americans and other victims has left in its wake a long trail of both casualties and question marks. Almost every day there is a mysterious new bombing, and often a previously unheard of group claims responsibility. Radical Governments in Libya, Syria and Iran often praise these attacks and, at the same time, insist they had nothing to do with them. What groups or states are behind these terrorist bombings? How are they connected? How are the terrorist gunmen or bombers recruited? How are the killings or bombings organized? And is this terrorism motivated by political grievances, or has it simply become another tool of international relations for some states? Evidence Remains Sketchy The evidence needed to answer these questions conclusively remains sketchy. But interviews in recent months with Arab, American and European diplomats in the Middle East and elsewhere, as well as with American, Arab and Israeli security experts, provide some clues about the terrorist forces that the United States and many of its allies are now facing.