RT Article T1 A dualistic vision: Robert Ezra Park and the classical ecological theory of social inequality JF The sociological quarterly VO 28 IS 3 SP 387 OP 411 A1 Helmes-Hayes, Richard C. 1951- LA English YR 1987 UL https://krimdok.uni-tuebingen.de/Record/1642123005 K1 Soziale Ungleichheit K1 Sozialforschung