Sebastião Rodrigues: International years of the quiet sun (design): Scientists still studying the results of a vast research program into solar activity and its influence on the earth: In 1964 and 1965, the world became one vast laboratory in which scientists from over 70 countries joined forces in a coordinated effort to learn more about solar-terrestrial relations. ("The Unesco courier", 4/2023)
country: Portugal
year: 1964
Yvert: 947
