Coba jelasin Lihat pula dari Kekekalan energi dong

{{cite book | author=Oxtoby & Nachtrieb | title=Principles of Modern Chemistry, 3rd ed. | publisher=Saunders College Publishing | year=1996 | id=}}

Stenger, Victor J. (2000). Timeless Reality. Prometheus Books. Especially chpt. 12. Nontechnical.