1. A cton F . S. 1959 A nalysis of straight line data. New Y ork: Jo h n W iley and Sons Inc.
2. M em;Burgess A.;Soc. Roy. Sci. Liege,1961
3. Burgess A. H um m er D. G. & Tully J . A. discussed b y B urke etal (1964 a). 1963 P riv ate com m unication. This work is