00637nam a2200193Ia 4500 CTU_97570 210402s9999 xx 000 0 und d 384.6 S631 Slack, Edward Robert The effect of the U. S. international telecommunications industry on the United States balance of payments Edward Robert Slack London University Microfilms International 1970 Telephone,Telecommunication policy United States,United States Trúc Trung tâm Học liệu Trường Đại học Cần Thơ