1. DNA insertions and gene structure;Williamson;Nature,1977
2. Why genes in pieces?;Gilbert;Nature,1978
3. Do genes-in-pieces imply proteins-in-pieces;Blake;Nature,1978
4. Proteins, exons, and molecular evolution. In Intervening sequences in evolution and development;Holland,1990
5. Speculations on the early course of evolution;Darnell,1986