Gaya APA

Rinto, I., Erny, Y. (2013). Keep smile (Cet. 1). Yogyakarta: Buku Pintar.

Gaya MLA

Rinto, Ipnu., Erny, Yulian. "Keep smile". Cet. 1 Yogyakarta: Buku Pintar, 2013. Text.