Some of Churchill 's pieces may infringe copyrights . For example , his 1981 serigraph Winter Attack was , according to Churchill and others , based on a 1972 drawing by the artist Thomas E. Mails Churchill printed 150 copies of Winter Attack and sold at least one of them . Other copies are available online for purchase . Churchill says that , when he produced Winter Attack , he publicly acknowledged that it was based on Mails ' work . The online journal Artnet mentions Churchill 's artwork and the controversy surrounding its originality .