RT Article T1 The Z-axis: Elevation gradient effects in urban America JF Regional science and urban economics VO 70 SP 312 OP 329 A1 Ye, Victor Yifan A2 Becker, Charles M. 1954- LA English YR 2018 UL https://krimdok.uni-tuebingen.de/Record/1912753944 DO 10.1016/j.regsciurbeco.2017.10.002