(1991)Internaional Conference on HF Radio Systems and Techniques 5th international conference on HF radio systems and techiques Internaional Conference on HF Radio Systems and Techniques (1971)International conference on large electric systems at high tension.(CIGRE) International Conference on HF Communication Systems and Techniques(3rd:1985) (1960)International Conference on Opertional Research Fifth international conference on radio receivers and associated systems. (1972)International Conference on Superalloys Processing (1979)International Conference on Verg Large Data Bases (1980)International Conference on Verg Large Data Bases