Complex sentence: Arnold Schlaet (1859--1946) was a U.S. oil industrialist and business man who, with Joseph S. Cullinan, co-founded Texaco Incorporated in 1902.
Split into simpler sentences: Arnold Schlaet (1859--1946) was a U.S. oil industrialist and business man. Schlaet, with Joseph S. Cullinan, co-founded Texaco Incorporated in 1902.