In 1963, Lichtenstein was parodying various types of sources such as commercial illustrations, comic imagery and even modern masterpieces. The masterpieces represented what could have been dubbed the "canon" of art and was thought of as "high art," while the "low-art" subject matter included comic strip images. His masterworks sources included the likes of Cézanne , Mondrian and Picasso . During this time in his career, Lichtenstein noted that "the things that I have apparently parodied I actually admire." [ 21 ] At the time, Lichtenstein was exploring the theme of "industrialization of emotion". In Lichtenstein's obituary, Los Angeles Times critic Christopher Knight said the work was "a witty rejoinder to De Kooning 's famously brushy paintings of women". [ 22 ] His comic romances often depicted stereotypical representations of thwarted passions. [ 23 ] Although the Lichtenstein Foundation website claims that Lichtenstein did not begin using his opaque projector technique until the fall of 1963, [ 24 ] Lichtenstein described his process for producing comics based art, including Drowning Girl :