By analyzing the file of the following URL, please teach me how to answer the following questions:

A Meta-analysis of the Price Elasticity of Gasoline Demand. A System of Equations Approach:

https://www.semanticscholar.org/paper/A-Meta-analysis-of-the-Price-Elasticity-of-Gasoline-Brons-Nijkamp/ba41c9c8f876a837b60dcda80b786b81b75f9a99

What statistical method have others used to answer your question?

Variables?

Functional form? Linear, exponential, other.

Geographies (region, country, supranational?)

Time length

Cross sectional

(Key words: "how to model demand for x")