buttons come and buttons go.

BELGRADE, Yugoslavia, Oct. 18—America's Apollo 11 astronauts received an enthusiastic welcome today as they arrived in the capital of Yugoslavia, the only Communist country they are visiting on their good- will tour around the world.

The astronauts, Neil A. Armstrong, Col. Edwin E. Aldrin and Col. Michael Collins, and their wives were greeted by tens of thousands of cheering people filling up the main streets of Belgrade and waving both American and Communist flags.

Belgrade, where the astronauts are spending two days, is the 12th stop on their world tour. Coming from Rome, they were welcomed at the Belgrade airport by members of the Yugoslav Government and other high ranking functionaries.

In bright sunshine, they drove in an open limousine from the airport to Mount Avala, where they laid a wreath at the memorial for the unknown soldier.

At noon, they were received by President Tito at the "White Palace," formerly the residence of the Yugoslav kings. During this meeting they received medals from Mr. Tito and were his guests at a luncheon given in their honor.

At the luncheon, Mr. Tito told the astronauts that all countries with the capacity and the means should jointly work on further conquering the universe because this was a common goal of all mankind.