This study is largely based upon the official trade statistics issued by the eight East European countries and the Soviet Union. This material is not always complete and, especially in the case of East Germany and Albania, is published with much delay. Hence it has not been possible to collect all information necessary for the discussion of trade in 1960; data pertaining to 1961 are provisional. There are inexplicable discrepancies between data furnished by the Soviet Union and those of other bloc countries, and information on some important fields of trade, such as uranium ore, is not available at all. Despite these drawbacks, the picture that emerges from the available material is clear enough and allows the researcher to present the main features and trends. Yugoslav trade statistics are, on the whole, satisfactory.
To avoid unnecessary repetition, the region comprising Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Rumania is often described as "six countries," or "seven countries" or "the area" if Albania is included. Trade with the Soviet Union is discussed on the basis of Soviet data. "National" data pertain to the six or seven countries. Quotations and footnotes are limited to matters of controversy. Figures in tables are rounded and therefore do not always add up to the totals given.
The literature of the subject is limited and dispersed. Apart from the official yearbooks and periodicals, a great deal of information is periodically issued by the United Nations in the "Economic Bulletin for Europe", published in Geneva. This source, however, must of necessity refrain from discussing the sensitive aspects of the problem. The many Soviet studies are too per-