Complex sentence: He has been called the most important historian of design since Nikolaus Pevsner (1902-1983), but, in contrast to Pevsner, he published a history of graphic design that went beyond nineteenth and twentieth centuries.
Split into simpler sentences: He has been called the most important historian of design since Nikolaus Pevsner (1902-1983). In contrast to Pevsner, he published a history of graphic design that went beyond the nineteenth and twentieth centuries.