TY  - BOOK
AU  - Erlander Sven
TI  - Optimal spatial interaction and the gravity models
T2  - Lecture notes in economics and mathematical system, 13
U1  - X4:75:(B), M0 
PY  - 1980///
CY  - Berlin
PB  - Springer Verlag         
KW  - Transport Economics -- United States
ER  -