The location of the historic city of Troy was finally pinned down by the researches of CARL BLEGEN , the detailed results of whose work have only recently become available. Also: The Exploding City - By A.D. 2,000 more than half the world's population may be living in cities. The population of some of them may exceeed 60 million. This is one of the main preoccupations of the World Institute of Ekistics, founded in London this month with Lord Llewelyn-Davies Architect, and Chairman of the Centre for Environmental Studies Constantinos Doxiadis.