Complex sentence: Wolfgang Rautenberg (1936 − September 4,2011) was a German mathematician and logician whose areas of research were model theory, non-classical logic, modal logic, temporal logic and self reference.
Split into simpler sentences: Wolfgang Rautenberg (1936 − September 4,2011) was a German mathematician and logician. His areas of research were model theory, non-classical logic, modal logic, temporal logic and self reference.