 Gallai was among the first to emphasize
min-max theorems and LP-duality in combinatorics.He is also known for his maximum theorem in optimization and for Berge's lemma, which states that a matching "M" in a graph "G" is maximum if and only if there is in "G" no augmenting path with respect to "M".In addition to mathematics, Claude Berge enjoyed literature, sculpture, and art.