37 CFR § 41.66 - Time for filing briefs.
(a) An appellant's brief must be filed no later than two months from the latest filing date of the last-filed notice of appeal or cross appeal or, if any party to the proceeding is entitled to file an appeal or cross appeal but fails to timely do so, no later than two months from the expiration of the time for filing (by the last party entitled to do so) such notice of appeal or cross appeal. The time for filing an appellant's brief or an amended appellant's brief may not be extended.
(b) Once an appellant's brief has been properly filed, any brief must be filed by respondent within one month from the date of service of the appellant's brief. The time for filing a respondent's brief or an amended respondent's brief may not be extended.
(e) No further submission will be considered and any such submission will be treated in accordance with § 1.939 of this title.