minor updates

Author: HumphreyYang

lectures/eigen_II.md

@@ -238,7 +238,7 @@ A = \begin{bmatrix} 0.5 & 0.1 \\
 \end{bmatrix}
 $$
 
-A here is also a primitive matrix since $A^k$ is everywhere positive for some $k \in \mathbb{N}$.
+$A$ here is also a primitive matrix since $A^k$ is everywhere positive for some $k \in \mathbb{N}$.
 
 
 $$
@@ -393,7 +393,7 @@ We are now prepared to bridge the languages spoken in the two lectures.
 
 A primitive matrix is both irreducible and aperiodic.
 
-So the Perron-Frobenius theorem explains why both the Imam and Temple matrix and Hamilton’s transition matrix (`mc_eg2`) converge to a stationary distribution — the Perron projection of the two matrices.
+So Perron-Frobenius theorem explains why both {ref}`Imam and Temple matrix <mc_eg3>` and {ref}`Hamilton matrix <mc_eg2>` converge to a stationary distribution, which is the Perron projection of the two matrices
 
 
 ```{code-cell} ipython3