Panofsky codified an influential approach to iconography in his 1939 "Studies in Iconology", where he defined it as "the branch of the history of art which concerns itself with the subject matter or meaning of works of art, as opposed to form," although the distinction he and other scholars drew between particular definitions of "iconography" (put simply, the identification of visual content) and "iconology" (the analysis of the meaning of that content), has not been generally accepted, though it is still used by some writers.