In 1961, upon an invitation of the State Department, he traveled through the U.S.A.; and —upon similar invitations— through the Soviet Union in 1963 and Bulgaria in 1965.
V 1961 dostal pozvanie ministerstva zahraničia USA a precestoval celé USA a na iné pozvanie zase precestoval Sovietsky zväz v roku 1963 a v roku 1965 Bulharsko.