 Some foundational results on classification were known in the 1950s.The result of , that holomorphic vector bundles on the Riemann sphere are sums of line bundles, is now often called the Birkhoff–Grothendieck theorem, since it is implicit in much earlier work of on the Riemann–Hilbert problem.The Riemann–Roch theorem for vector bundles was proved by , before the 'vector bundle' concept had really any official status.