38 CFR 20.404: Rule 404. Time limit for response to appeal by another contesting party in a simultaneously contested claim.

A party to a simultaneously contested claim may file a brief, argument, or request for a different type of review under § 20.202(b) in answer to a Notice of Disagreement filed by another contesting party. Any such brief, argument, or request must be filed with the Board within 30 days from the date the content of the Notice of Disagreement is furnished as provided in § 20.403. Such content will be presumed to have been furnished on the date of the letter that accompanies the content.