 Nineteenth-century Quellenforschung was especially interested in his Commentary on the Physics, which was edited in two volumes (Simplicii in Aristotelis Physicorum libros quattuor priores/quattuor posteriores, comprising almost 1500 pages) by Hermann Diels; this commentary served as the basis for Diels’ edition of the Doxographi Graeci (Greek Doxographers), which includes the main doctrines on natural philosophy according to ancient doxographical compendia.