VNCN, chapter 13 (Conformance), page 221

     Let `CT' be a reference type of base class  `C',  and
     `BT'  be  a type whose base class `B' is not generic.
     `CT' conforms directly to `BT' if  and  only  if  the
     Inheritance clause of `C' lists `B' in one or more of
     its Parent items.