Spencer, H. (1969). The Penrose annual 1969: The international review of the graphic arts. Lund Humphries.
Citazione stile Chigago Style (17a edizione)Spencer, Herbert. The Penrose Annual 1969: The International Review of the Graphic Arts. Londres: Lund Humphries, 1969.
Citatione MLA (9a ed.)Spencer, Herbert. The Penrose Annual 1969: The International Review of the Graphic Arts. Lund Humphries, 1969.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.