Robertson, W. C. (2002). Energy. NSTA Press.
Lua i Stíl Chicago (17ú heag.)Robertson, William C. Energy. Arlington, Va.: NSTA Press, 2002.
Lua MLA (9ú heag.)Robertson, William C. Energy. NSTA Press, 2002.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.