René Thom publishes in 1954, in Commentarii Mathematici Helvetici, "Quelques propriétés globales des variétés différentiables", the paper founding cobordism theory in differential topology. The theory classifies manifolds according to equivalence relations based on their shared boundaries and becomes one of the central tools of algebraic topology in the second half of the 20th century, with later applications extending as far as the catastrophe theory Thom himself developed in the 1970s. Thom received the Fields Medal in 1958, shared with Klaus Roth.