Before revision:  Endogenous agglomeration emerges when inter-regional trade and/or social interactions incur high transportation costs, and the uniform dispersion occurs when these costs become negligibly small (i.e., when distance dies).
After revision:  Endogenous agglomeration emerges when inter-regional trade and/or production externalities incur high transportation costs, and the uniform dispersion occurs when these costs become negligibly small (i.e., when distance dies).