... constants

The resulting model is often called origin-destination constrained gravity model.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... technique 

For a good discussion on the maximum likelihood technique of estimation one may refer to any good book on statistics or econometrics; for example Gujarati [#!guj1!#] or Wonnacott and Wonnacott [#!won1!#] may be referred.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.