Congress. The party saw its political unity and strong discipline as conditions for its ideological zeal. Between 1946 and 1980, the party's headquarters was in Felix Meritis in Amsterdam. Linked and pillarized organisations The party had a small, but strong communist pillar around it. Important organizations were the communist trade union, the Rode Vakcentrale (Red Trade Union) before 1940 and the Eenheidsvakcentrale (Unity Trade Union) between 1945 and 1960, and the party's paper, De Tribune (the Tribune) before 1940 and De Waarheid (The Truth), which was founded as a resistance paper and named after its Soviet counterpart after 1940. The party's youth organization was the formally independent General Dutch Youth League. The party's scientific organization was the Instituut voor Politiek en Sociaal Onderzoek (Institute for Political and Social Research) which published Politiek en Cultuur (Politics and Culture). The CPN had its own publisher called . International organisations Since 1918 the party was a member of the Third International, first in the form of the Comintern, and after 1947 in the Cominform. Relationships to other parties For a long time the Communists were methodically isolated, partially because of its revolutionary ideology and partially because of the antagonistic style of its politics. The communists used this style to prevent its electorate from moving to its competitors. The relationship between the Social Democratic Workers' Party (before the Second World War) and the PvdA (after the Second World War) was always troublesome. The SDP split from the SDAP over ideological differences, orthodox Marxist, revolutionary politics versus revisionist and reformist politics. The social-democrats saw the communists as insignificant while the communists taunted the social-democrats by calling them "servants to capitalism" and "social fascists". During the Cold War, the PvdA embraced Atlanticism, NATO and the alliance with the United States, while the CPN advocated stronger links with the USSR. The PvdA had the strongest anti-communists in its ranks. During the 1970s when a more radicalized PvdA advocated a large progressive coalition, they still excluded the CPN. The relationship between leftwing splinter groups and the communists was notoriously bad. The CPH ignored the Revolutionary Socialist Party during its four-year term in the 1930s. The Pacifist Socialist Party, which was partially composed of those expelled from the CPN, was denounced as a party of agents of the U.S. Central Intelligence Agency. The CPN methodically voted against proposals of the PSP, even when they supported them. In the 1980s