43 CFR §3837.24

1. (a)If you gave written notice to the delinquent co-claimant by personal service, you must sign and submit a notarized affidavit explaining how and when you delivered the written notice to the delinquent co-claimant.
2. (b)If you gave written notice to the delinquent co-claimant by mail, you must submit:
   1. (1)A copy of the notice you mailed to the delinquent co-claimant; and
   2. (2)A copy of the signed U.S. Postal Service return receipt from the registered or certified envelope in which you sent the notice to the delinquent co-claimant.
3. (c)If you published the notice in a newspaper, you must submit:
   1. (1)A statement from the newspaper publisher or the publisher's authorized representative describing the publication, including the beginning and ending dates of publication;
   2. (2)A printed copy of the published notice; and
   3. (3)A notarized affidavit attesting that you conducted a diligent search for the delinquent co-claimant, you could not locate the delinquent co-claimant, and therefore notification by publication was necessary.