diff --git a/doc/crypto/X509_NAME_get_index_by_NID.pod b/doc/crypto/X509_NAME_get_index_by_NID.pod
index 3b1f9ff43b65a07e120b541a5818bb05d793171d..c8a8128795614982525dba7c05a9b1afca246b23 100644
--- a/doc/crypto/X509_NAME_get_index_by_NID.pod
+++ b/doc/crypto/X509_NAME_get_index_by_NID.pod
@@ -59,6 +59,10 @@ X509_NAME_get_index_by_OBJ() should be used followed by
 X509_NAME_get_entry() on any matching indices and then the
 various B<X509_NAME_ENTRY> utility functions on the result.
 
+The list of all relevant B<NID_*> and B<OBJ_* codes> can be found in
+the source code header files E<lt>openssl/obj_mac.hE<gt> and/or
+E<lt>openssl/objects.hE<gt>.
+
 =head1 EXAMPLES
 
 Process all entries: