The authors later transferred all their intellectual property rights, including the copyright of the MMSE, to MiniMental registering the transfer with the U.S. Copyright Office on June 8, 2000. In March 2001, MiniMental entered into an exclusive agreement with Psychological Assessment Resources granting PAR the exclusive rights to publish, license, and manage all intellectual property rights to the MMSE in all media and languages in the world. Despite the many free versions of the test that are available on the internet, PAR claims that the official version is copyrighted and must be ordered only through it. At least one legal expert has claimed that PAR's copyright claims are weak. The enforcement of copyright on the MMSE has been compared to the phenomenon of "stealth" or "submarine" patents, in which a patent applicant waited until an invention gained widespread popularity before allowing the patent to issue, and only then commenced enforcement. Such applications are no longer possible, given changes in patent law. The enforcement of the copyright has led to researchers looking for alternative strategies in assessing cognition.