The structure has evolved over time and may vary by state.

The short answer is that we cannot, and that structures of this kind do not in fact evolve.

The structure has evolved and forms the basis for energy and other projects throughout the world.

A complex structure of relationships evolved, growing into a new awareness.

He explained that the structure evolved because the group needed equity to finance growth.

From the 1880s, the structure of the army has evolved with changing defence needs and financial constraints.

A new social structure evolved: when sons married, they would remain in the same house; such an extended family was a clan.

The social structure of the family had evolved quickly because it was the most efficient way to ensure its survival.

The show's structure evolved over time and included several regular segments that appeared in almost every episode.