2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/62409This is the survey of results about norm one projections and 1-complemented subspaces in Köthe function spaces and Banach sequence spaces. The historical development of the theory is presented from the 1930's to the newest ideas. Proofs of the main results are outlined. Open problems are also discussed. Every effort has been made to include as complete a bibliography as possible.54 pagesFunctional Analysis46B, 46Etext