TY - PROGRESS IN GEOGRAPHY A1 - T1 - Y1 - 1988-04-25 00:00:00.0 JF - PROGRESS IN GEOGRAPHY JO - PROGRESS IN GEOGRAPHY SP - 57 EP - 59 VL - 7 IS - 2 UR - {https://www.progressingeography.com/EN/10.11820/dlkxjz.1988.02.017} N1 - 10.11820/dlkxjz.1988.02.017 ER -