https://id.wikipedia.org/wiki/Argumen_periapsis
Argumen periapsis - Wikipedia bahasa Indonesia, ensiklopedia bebas
bahasa indonesiaargumenwikipediaensiklopediabebas
https://scp-wiki.wikidot.com/scp-4391
Periapsis - SCP Foundation
The SCP Foundation's 'top-secret' archives, declassified for your enjoyment.
scpfoundation