WILLIAMS, G. A., BOLEN, M. C., & DOERHOFF Ray B. (1973). Challenges to science physical science. Wbster Division, McGraw-Hill Book Company.
Lua i Stíl Chicago (17ú heag.)WILLIAMS, George A., Max C. BOLEN, agus DOERHOFF Ray B. Challenges to Science Physical Science. New York: Wbster Division, McGraw-Hill Book Company, 1973.
Lua MLA (9ú heag.)WILLIAMS, George A., et al. Challenges to Science Physical Science. Wbster Division, McGraw-Hill Book Company, 1973.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.