Original: His position at Cowles gave Phelps the chance to interact with Arthur Okun and other notables in the field. He was able to collaborate with other top economists working on growth theory, including David Cass and fellow Nobelist Tjalling Koopmans.
Simplified: Work at the Cowles Foundation gave Phelps the chance to meet with other important economists who were working on growth theory, such as David Cass and Nobel Prize winner Tjalling Koopmans.