Minnesota Form 128. Appellant's Formal Brief and Addendum is a form used by appellants in the Minnesota court of appeals. It is a document that contains the appellant's arguments and legal authority in support of the appeal. There are two types of Minnesota Form 128. Appellant's Formal Brief and Addendum: either a Formal Brief or an Addendum. The Formal Brief is the main legal document that outlines the appellant's arguments and the legal authority in support of the appeal. The Addendum is an optional document that can be used to supplement the Formal Brief with additional legal argument or authority.