(1) A third party may intervene in revocation or invalidity proceedings if a final decision on the application for revocation or a declaration of invalidity has not yet been taken and if the third party can substantiate that
1. proceedings for infringement of the same registered trade mark are pending against him; or
2. he was required to cease and desist from an alleged infringement of the same registered trade mark.
The intervention may be requested within three months from initiating proceedings pursuant to sentence (1) no. (1) or from receipt of the request to cease and desist pursuant to sentence (1) no. (2).
(2) For filing the request, section 53 (1) to (3) shall apply accordingly. If the intervention occurs in appeal proceedings before the Federal Patent Court, the intervening party shall become a party to the appeal.