What were foreigners in the roman army known as?

Articles of the confederation is a good representation of a system of government.

Carbon tetrachloride is a toxic liquid. a carbon tetrachloride molecule has one atom of carbon and four atoms of chlorine. what is its chemical formula?

Why are the majority of the world's economies mixed? what may happen to the "pure" types of economies (traditional, socialist/command, market capitalist) when they incorporate elements from other economic models?