/PRODUCER=(producer-name[,...])

    Selects software products that the specified manufacturer
    produces.

    Note that the PRODUCT SHOW HISTORY command allows you to specify
    both the /PRODUCER and /PRODUCT qualifiers, which you need to
    spell out because they are not unique within the first four
    characters.

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