The third stage, which the government called the "completion of the construction of the material and technical basis of socialism," saw further industrialization and agricultural growth, aided largely by Mongolia's joining the Council for Mutual Economic Assistance (Comecon) in 1962. After the Sino-Soviet split, Chinese aid ceased, but continued Soviet and East European financial and technical assistance in the forms of credits, advisers, and joint ventures enabled Mongolia to modernize and to diversify industry, particularly in mining. New industrial centers were built in Baganuur, Choibalsan, Darkhan, and Erdenet, and industrial output rose significantly. Although animal husbandry was stagnant, crop production increased dramatically with the development of virgin lands by state farms. Foreign trade with Comecon nations grew substantially. Transportation and communications systems were improved, linking population and industrial centers and extending to more remote rural areas. In the late 1980s, Mongolia had developed into an agricultural-industrial economy, but the shortcomings of the mongolian economy and the example of perestroika in the Soviet Union led Mongolian leaders to undertake a reform program to develop the economy further in a more capitalistic direction.