Creswell, John W.
SAGE Publications, 2018
Buku Teks
Patton, Michael Quinn
Sage, 1990
Buku Teks SO
Norman K. Denzin, editor; Yvonna S. Lincoln, editor
Sage Publications, 2003
Buku Teks SO
Strauss, Anselm L.
Cambrigde University Press, 1987
Buku Teks SO
Allen, T. Harrell
Praeger, 1978
Buku Teks