al, S. .. e. Teknik sampling. Gramedia Pustaka Utama.
Chicago Style (17th ed.) Citational, Sugiarto ... et. Teknik Sampling. Gramedia Pustaka Utama.
MLA (8th ed.) Citational, Sugiarto ... et. Teknik Sampling. Gramedia Pustaka Utama.
Warning: These citations may not always be 100% accurate.