"Credo". Essay by Arthur C. Clarke (1991), later published in Arthur C. Clarke "Greetings, Carbon-Based Bipeds!: Collected Essays, 1934-1998" (p. 360), 1990.
Charles Brock, Charles Sheeler, National Gallery of Art (U.S.), Art Institute of Chicago, M.H. De Young Memorial Museum (2006). “Charles Sheeler: across media”, University of California Press