diff --git a/trex.org b/trex.org
index 3c57e82..813820c 100644
--- a/trex.org
+++ b/trex.org
@@ -401,10 +401,9 @@ prim_factor =
   construction of all the angular functions of each shell.  We
   consider two cases for the angular functions: the real-valued
   spherical harmonics, and the polynomials in Cartesian coordinates.
-  In the case of spherical harmonics, the AOs are ordered in
-  increasing magnetic quantum number ($-l \le m \le l$), and in the case
-  of polynomials we impose the canonical ordering of the
-  Libint2 library, i.e
+  In the case of spherical harmonics, the AOs are ordered as
+  $0, +1, -1, +2, -2, \dots, +m, -m$ and in the case of polynomials we
+  impose the canonical (or alphabetical) ordering), i.e
 
   \begin{eqnarray}
   p & : & p_x, p_y, p_z \nonumber \\
@@ -413,6 +412,9 @@ prim_factor =
   {\rm etc.} \nonumber
   \end{eqnarray}
 
+  Note that there is no exception for $p$ orbitals in spherical
+  coordinates: the ordering is $0,+1,-1$ which corresponds $p_z, p_x, p_y$.
+
   AOs are defined as
 
   \[