Barbara Hepworth, Oblique Forms, 1969In 1968, under the guidance of lithographer Stanley Jones, Barbara Hepworth produced a suite of works known as Twelve Lithographs. This series was a huge commercial success. Hepworth described how this was an opportunity to work on ideas that would eventually translate into sculpture. Between 1967 and 1970 Hepworth made various sculptures on the same subject of oblique forms.