diff --git a/zfit_physics/models/pdf_erfexp.py b/zfit_physics/models/pdf_erfexp.py
index 6917a6c..3dc1a80 100644
--- a/zfit_physics/models/pdf_erfexp.py
+++ b/zfit_physics/models/pdf_erfexp.py
@@ -28,6 +28,8 @@ def erfexp_pdf_func(x, alpha, beta, gamma, n):
     return tf.math.erfc((x - alpha) * beta) * znp.exp(-gamma * (znp.power(x, n) - znp.power(alpha, n)))
 
 
+# Note: There is no analytic integral for the ErfExp PDF
+# We tried with sympy, Mathematica, Wolfram Alpha and https://www.integral-calculator.com/
 class ErfExp(zfit.pdf.BasePDF):
     _N_OBS = 1