Gaya APA

, ., Walker, O, H. (1995). Astronomical: 44 activities, experiments, and projects . USA: USA: J.Weston Walch, 1995.

Gaya MLA

, ., Walker, Ormiston, H. "Astronomical: 44 activities, experiments, and projects". USA: USA: J.Weston Walch, 1995, 1995. Text.