Conversation so far:
what did Nolan Ryan do later in life?
Nolan Ryan's post-retirement business interests include ownership of two minor league teams
what are the 2 minor league teams Nolan Ryan owns?
Nolan Ryan owned the Corpus Christi Hooks, which play in the Class AA Texas League, and the Round Rock Express, a Class AAA team in the Pacific Coast League.

Question: when did he retire from playing?
Self-contained rewrite: when did Nolan Ryan retire from playing?