diff --git a/README.md b/README.md
index 736aeef..79967fb 100644
--- a/README.md
+++ b/README.md
@@ -35,7 +35,9 @@ pip install .
 
 Please refer to [mech2d](https://doi.org/10.3390/molecules28114337)
 The polar plot of Young's modulus and Poisson's ratio is obtained by following equation:
-$$v_{zz} & = \frac{C_{12}}{C_{22}} \\
+$$
+\begin{align*}
+v_{zz} & = \frac{C_{12}}{C_{22}} \\
 d_1 & = \frac{C_{11}}{C_{22}} + 1 - \frac{C_{11} C_{22} - C_{12}^2}{C_{22} C_{66}} \\
 d_2 & = -\left(2 \frac{C_{12}}{C_{22}} - \frac{C_{11} C_{22} - C_{12}^2}{C_{22} C_{66}}\right) \\
 d_3 & = \frac{C_{11}}{C_{22}} \\
@@ -43,7 +45,8 @@ Y_{zz} & = \frac{C_{11} C_{22} - C_{12}^2}{C_{22}} \\
 \theta & \in [0, 2\pi] \text{ with 360 points} \\
 E(\theta) & = \frac{Y_{zz}}{\cos(\theta)^4 + d_2 \cos(\theta)^2 \sin(\theta)^2 + d_3 \sin(\theta)^4} \\
 V(\theta) & = \frac{v_{zz} \cos(\theta)^4 - d_1 \cos(\theta)^2 \sin(\theta)^2 + v_{zz} \sin(\theta)^4}{\cos(\theta)^4 + d_2 \cos(\theta)^2 \sin(\theta)^2 + d_3 \sin(\theta)^4}
-\en$$
+\end{align*}
+$$
 
 ## Usage