Certificate of Registration and Ownership Documents

If the Certificate of Registration is not proof of ownership of a small airplane, what document(s) might exist that would reflect the true ownership of an airplane?

It's my understanding that a "title" does not exist. What document(s) does the FAA rely upon to issue a Certificate of Registration when an airplane is sold by an individual to another individual, other than a Bill of Sale?

ANSWER: Evidence of ownership can be shown on an AC Form 8050-2, Aircraft Bill of Sale, or similarly worded document. For the purpose of registration, the “Bill of Sale” is the document used by the FAA to confirm that the applicant is the registered owner.