diff --git a/vector.hpp b/vector.hpp
index 98b236e2..84f61af7 100644
--- a/vector.hpp
+++ b/vector.hpp
@@ -86,7 +86,8 @@ namespace util {
     }
 
     // convert vector in cartesian coordinates (x,y,z) to spherical
-    // coordinates (r,inclination,azimuth) with theta inclination and phi azimuth.
+    // coordinates (using ISO convention: r,inclination,azimuth) with theta
+    // inclination and phi azimuth.
     template <typename T>
     constexpr vector<3,T>
     cartesian_to_spherical (vector<3,T> c)