2310.3 (D) (2) Signature Requirements
The notice of termination must be signed by each author who is terminating the grant or by his or her duly authorized agent.
If an author is deceased the notice must be signed by the required number and proportion of the owners of that author’s termination interest or by their duly authorized agents. In addition, the notice shall contain a brief statement specifying each person’s relationship to the deceased author, such as “widow,” “widower,” “child,” or “grandchild.”
If the notice is signed by a duly authorized agent, the notice shall clearly identify the person or persons that the agent represents.
In all cases, the notice should contain a handwritten signature and a typewritten or legibly hand printed statement containing the full name and address of each party or agent who signed the notice.
37 C.F.R. § 201.10 (C) (3)- (5).