1. The constant comparative method of qualitative analysis;BG Glaser;Soc Probl,1965
2. The discovery of grounded theory: Strategies for qualitative research;BG Glaser,1967
3. Naturalistic inquiry;YS Lincoln,1985
4. Qualitative Nursing Research: A Contemporary Dialogue;JM Morse,1989
5. Sample size in qualitative research;M Sandelowski;Res Nurs Health,1995