29 C.F.R. § 102.21
An original and four copies of the answer shall be filed with the Regional Director issuing the complaint. Immediately upon the filing of the answer, Respondent shall serve a copy thereof on the other parties. An answer of a party represented by counsel or non-attorney representative shall be signed by at least one such attorney or non-attorney representative of record in his/her individual name, whose address shall be stated. A party who is not represented by an attorney or non-attorney representative shall sign his/her answer and state his/her address. Except when otherwise specifically provided by rule or statute, an answer need not be verified or accompanied by affidavit. The signature of the attorney or non-attorney party representative constitutes a certificate by him/her that he/she has read the answer; that to the best of his/her knowledge, information, and belief there is good ground to support it; and that it is not interposed for delay. If an answer is not signed or is signed with intent to defeat the purpose of this section, it may be stricken as sham and false and the action may proceed as though the answer had not been served. For a willful violation of this section an attorney or non-attorney party representative may be subjected to appropriate disciplinary action. Similar action may be taken if scandalous or indecent matter is inserted.
29 C.F.R. §102.21