diff --git a/pyerrors/__init__.py b/pyerrors/__init__.py
index d7108dfb..c9792e18 100644
--- a/pyerrors/__init__.py
+++ b/pyerrors/__init__.py
@@ -82,7 +82,7 @@ my_sum.details()
 ```
 
 We use the following definition of the integrated autocorrelation time established in [Madras & Sokal 1988](https://link.springer.com/article/10.1007/BF01022990)
-$$\tau_\mathrm{int}=\frac{1}{2}+\sum_{t=1}{W}\rho(t)$$
+$$\tau_\mathrm{int}=\frac{1}{2}+\sum_{t=1}^{W}\rho(t)\geq \frac{1}{2}$$
 The window $W$ is determined via the automatic windowing procedure described in [arXiv:hep-lat/0306017](https://arxiv.org/abs/hep-lat/0306017)
 The standard value for the parameter $S$ of this automatic windowing procedure is $S=2$. Other values for $S$ can be passed to the `gamma_method` as parameter.