olemus
nimeksteisenduse kirje domeeninimede süsteemis
= a reverse resolving conversion record in the Domain Name System

ülevaateid
https://joker.com/faq/content/11/508/en/what-are-_ptr-records_.html

https://www.immagic.com/eLibrary/ARCHIVES/GENERAL/WIKIPEDI/W120423L.pdf

https://www.cloudns.net/wiki/article/40/

näiteid
https://docs.oracle.com/cd/E19683-01/806-4077/dnsintro-160/index.html

standardid
http://tools.ietf.org/html/rfc1035#page-12