Complex sentence: Columbia again revived the label in 1940 after they lost the rights to the Vocalion name (by dropping the Brunswick label) and pressed it until 1946; it was revived in the 1950's and used sporadically through the 1990s.
Split into simpler sentences: Columbia again revived the label in 1940 after they lost the rights to the Vocalion name (by dropping the Brunswick label) and pressed it until 1946. It was revived once again in the 1950's and used sporadically through the 1990s.