When a return, form, or other document called for under this part is required by this part or in the instructions on or with the return, form, or other document to be executed under penalties of perjury, it shall be so executed, as defined in subpart B of this part, and shall be signed by the proprietor, or other duly authorized person.

(68A Stat. 749 (26 U.S.C. 6065))