VGCP, chapter 18 (Creating objects), page 285

     Creation_clause rule

     A Creation_clause appearing in the Creators part of a
     class  `C'  is  valid if and only if it satisfies the
     following four conditions, the last three  for  every
     Feature_identifier    `fname'    in    the   clause's
     Feature_list:

        1 `C' is effective.

        2 `fname' is the final name of a procedure of `C'.

        3 `fname' appears only once in the Feature_list.

        4 If  `C'  is  expanded,  that  procedure  has  no
          arguments,   and   no  other  Feature_identifier
          appears in the Feature_list.