Polak, F. L., & Boulding, E. (1973). The image of the future. Elsevier Scientific Pub.
Lua i Stíl Chicago (17ú heag.)Polak, Frederik Lodewijk, agus Elise Boulding. The Image of the Future. Amsterdam: Elsevier Scientific Pub, 1973.
Lua MLA (9ú heag.)Polak, Frederik Lodewijk, agus Elise Boulding. The Image of the Future. Elsevier Scientific Pub, 1973.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.