Complex sentence: The first Kock pouches were not created with any type of valve mechanism and required additional development, work which Kock continued to advance through further experimentation into the 1970s and 1980s.
Split into simpler sentences: The first Kock pouches were not created with any type of valve mechanism. The procedure required additional development, work which Kock continued to advance through further experimentation into the 1970s and 1980s.