Nicolson, Iain
The universe
Horus Editions, 1995
Buku Referensi
Abell, George O.
Exploration of the universe
Holt Rinehart and Winston, 1974
Buku Teks
Exploration of the universe
Buku Teks
Koupelis, Theo
In quest of the universe
Jones & Bartlett learning, 2011
Buku Teks
The universe grasper
Artikel Jurnal