Gaya APA

Purba, R, H. (2007). The use of Progressive Tense in Sports Game . : Universitas Muhammadiyah Sumatera Utara.

Gaya MLA

Purba, Ria, Hafni. "The use of Progressive Tense in Sports Game". : Universitas Muhammadiyah Sumatera Utara, 2007. .