Artists leave behind incomplete work for a variety of reasons. A piece may not be completed if the subject becomes unavailable, such as in the changing of a landscape or the death of a person being painted. Elizabeth Shoumatoff's "Unfinished Portrait" of 32nd U.S. president Franklin D. Roosevelt was started around noon on 12 April 1945 but left unfinished when Roosevelt died later that day. In other instances, outside circumstances can prevent the execution of an otherwise "finished" artwork: Leonardo da Vinci developed sketches and models for the "Gran Cavallo" horse statue but the bronze to cast the sculpture was diverted to make cannons. Five hundred years later, two full-size sculptures were completed based on Leonardo's work. Technically his "The Last Supper" is unfinished. In most pictures it shows a roof, but at Milan, where the painting lies, it shows some Latin that is half done. Robert William Buss left unfinished his most famous painting, "Dickens' Dream", just as Charles Dickens himself had left a novel half-complete at his death.