VMS Help PRODUCT, SHOW, PRODUCT, Qualifiers, /REFERENCED_BY  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /REFERENCED_BY=(product-name[,...])

    Displays products that are referenced by the named product.
    Use this qualifier to show if the product, specified in the
    /REFERENCED_BY qualifier, has a software dependency on the
    product or products specified in the product-name parameter of
    the PRODUCT SHOW PRODUCT command. If you specify an asterisk (*)
    as the product name, all referenced products are listed for the
    product named in the /REFERENCED_BY qualifier.

    Parentheses (())  are optional only when you specify a single
    product name. They are required when you specify multiple product
    names.

    To list all products that require a specified product to be
    installed, use the command:

    PRODUCT SHOW PRODUCT product-name /FULL /REFERENCED_BY=*

    To list all products that are referenced by (that is, required
    by) a particular product, use the command:

    PRODUCT SHOW PRODUCT * /REFERENCED_BY=product-name

    To list all products that are referenced by (that is, required
    by) other products, use the command:

    PRODUCT SHOW PRODUCT * /REFERENCED_BY=*