VNCG, chapter 13 (Conformance), page 222

     Let `BT' be a generically derived reference  type  of
     base  type  B  [`X1, ... Xn'] for some `n >= 1', where
     the  formal  generic  parameters  of  `B'  are   `G1,
     ... Gn'.   Let `CT' be a reference type of base class
     `C' different from `B'.  To  determine  whether  `CT'
     conforms  directly  to  `BT', define the substitution
     `sigma' as follows:

       If `CT' is non-generic,  `sigma'  is  the  identity
          substitution.

       If `CT' is a a generically  derived  type,  of  the
          form C [`Y1, ... Ym'], and class `C' is declared
          with formal  generic  parameters  `H1,  ... Hm',
          then  `sigma'  applied  to  any of the `Hi' (for
          `1 <= i <= m') is `Yi', and `sigma' applied to any
          other element is the element itself.

          Then `CT' conforms directly to `BT' if and  only

          if  the  Inheritance clause of `C' lists B [`Z1,
          ... Zn'] as one of its  Parent  items  and,  for
          every   `j'   such  that  `1 <= j <= n',  applying
          substitution `sigma' to `Zj' yields `Xj'.