diff --git a/src/11_nearly_free_electron_model_solutions.md b/src/11_nearly_free_electron_model_solutions.md
index 020da00e0aa1aedb4ba2fdaad376c5d0ef824730..f21e73b3b4545dec0732432fa00d671528700432 100644
--- a/src/11_nearly_free_electron_model_solutions.md
+++ b/src/11_nearly_free_electron_model_solutions.md
@@ -155,7 +155,7 @@ $$
 $$
 where $\langle n-1|n\rangle$ is the overlap between two neighbouring wavefunctions:
 $$
-\langle n-1|n\rangle$ = 2\kappa\int_0^\infty e^{-\kappa|x-a/2|}e^{-\kappa|x+a/2|} = e^{-\kappa a}(1+\kappa a)
+\langle n-1|n\rangle = 2\kappa\int_0^\infty e^{-\kappa|x-a/2|}e^{-\kappa|x+a/2|} = e^{-\kappa a}(1+\kappa a)
 $$
 and
 $$