When talking politics, however, the French, like the Americans, tend to go for the more formal notion of justice.

ECONOMIST: Bad language

Formal proof is a notion developed in the early part of the 20th century by logicians such as Bertrand Russell and Gottlob Frege, along with mathematicians such as David Hilbert (who can fairly be described as the father of modern mathematics) and Nicolas Bourbaki, the pseudonym of a group of French mathematicians who sought to place all of mathematics on a rigorous footing.

ECONOMIST: Just what does it mean to prove something?

At its core it pledges the notion that the informal economy is made up of marginal activities that are distinct and largely unrelated to the formal sector.

FORBES: Informality: A Marker Of Opportunity