diff --git a/book/_toc.yml b/book/_toc.yml
index c32cf7aeaecffc458e06f5753609c53fa43c1aa5..618f202e063b1c14ba070c83912515dce78fe956 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -138,7 +138,6 @@ parts:
       - file: fem/poisson2d.md
       - file: fem/isoparametric_mapping.md
 
-    # START REMOVE-FROM-PUBLISH
     - file: signal/intro.md
       title: Signal Processing
       sections:
@@ -159,7 +158,6 @@ parts:
         title: Spectral Estimation
       - file: signal/videos
         title: Supplementary Videos
-    # END REMOVE-FROM-PUBLISH
 
     # START REMOVE-FROM-PUBLISH
     - file: time_series/intro.md
diff --git a/book/fem/shape.md b/book/fem/shape.md
index 62296a67091cad516a3a659d96a6b4a5b397579d..e58b1106af6a44a769963bbdbc1d5bd68dc6eebb 100644
--- a/book/fem/shape.md
+++ b/book/fem/shape.md
@@ -160,7 +160,7 @@ The 9-node quadrilateral element
 A popular alternative is one where the center node is removed, resulting in an 8-node quadrilateral element with the following shape function:
 
 $$
-N_i=a_i+b_ix+c_iy+d_ix^2+e_ixy+f_iy^2+g_ix^2y+h_ixy
+N_i=a_i+b_ix+c_iy+d_ix^2+e_ixy+f_iy^2+g_ix^2y+h_ixy^2
 $$
 
 
diff --git a/book/fvm/fvm.ipynb b/book/fvm/fvm.ipynb
index a7cc6bc262c19dd1e9106587680e7a9a4bebdac6..3d306521d4061e9c5d2fa4e85e47cca03fc60e2a 100644
--- a/book/fvm/fvm.ipynb
+++ b/book/fvm/fvm.ipynb
@@ -143,7 +143,7 @@
     "After applying the Divergence Theorem, we arrive at:\n",
     "\n",
     "$$\n",
-    "\\epsilon_0 \\int_{S} \\mathbf{n} \\cdot \\mathbf{E} dS = \\int_{S} \\rho dS\n",
+    "\\epsilon_0 \\int_{S} \\mathbf{n} \\cdot \\mathbf{E} dS = \\int_{V} \\rho dV\n",
     "$$\n",
     "\n",
     "\n",