harvtxt error: no target: CITEREFKesten1982 (help))。另一种已知精确解的特殊情况是贝特晶格(英语:Bethe_lattice)(该模型的每一个顶点有z个近邻顶点,如此延伸,没有回路), p c = 1 z − 1 {\displaystyle p_{c}={\frac
Scientifique de Bruxelles, Vol. 47, p. 49, April 1927 Alpher, R. A., H. Bethe and G. Gamow. “The Origin of Chemical Elements,” Physical Review, 73, Issue