source: http://www.chem.arizona.edu/~salzmanr/480a/480ants/gibbspr/gibbspr.html
找了很久才找到真正詳細易懂的證明,
本文章適合修讀過熱力學,物理化學或材料熱力學等課程的人來閱讀
Let's try to motivate the Gibbs phase rule. Consider a typical "one−component phase diagram".(單化合物相圖)
(P-T diagram; p indicates phase[在該點有幾相], and v indicates variance[變數的數目] )
