Complex sentence: Rich in oil, it produces 60% of total Angolan production and international corporations such as Chevron Corporation, Total and Agip operate in the country, as well as partially state-owned Sonangol, a key corporation for Angola.
Split into simpler sentences: Rich in oil, it produces 60% of the total Angolan output and international corporations such as Chevron Corporation, Total and Agip operate in the country. So does the partially state-owned Sonangol, a key corporation for Angola.