A. Zahroni, D. B. Z. Siahaan, MM, and D. C. Rustana, Ph.D, “PERBANDINGAN HASIL BELAJAR FISIKA SISWA KELAS X YANG DIAJARKAN MODEL GROUP INVESTIGATION DENGAN MODEL TWO STAY TWO STRAY”, PROSIDING SNF, vol. 4, pp. SNF2015-I, Oct. 2015.