Birks, M., & Mills, J. (2015). Grounded theory: a practical guide (2nd ed.). London: Sage.
An accessible user-friendly guide to grounded theory. Particularly suited to the novice Grounded Theorist, the book compares and contrasts the different interpretations of grounded theory and covers the whole research process from planning through to evaluation, dissemination and maximising impact.
Charmaz, K. (2014). Constructing grounded theory (2nd ed.). London: Sage.
Constructivist grounded theory in which theory is co-constructed.
Corbin, J., & Strauss, A. L. (2015). Basics of qualitative research: techniques and procedures for devleoping grounded theory. London: Sage.
Glaser, B. G., & Strauss, A. L. (1967). The discovery of grounded theory: strategies for qualitative research. Chicago: Aldine Publishing Company.
Classical grounded theory in which theory is discovered.
Combining Approaches to Research
Johnson, L. (2014). Adapting and combining constructivist grounded theory and discourse analysis: a practice guide for research. International Journal of Multiple Research Approaches, 8(1), 110-116.
Provides a worked example of the process of using constructivist grounded theory and discourse analysis within a research project.
Ontology and Epistemology
Ralph, N., Birks, M., Chapman, Y. (2015). The methodological dynamism of grounded theory. International Journal of Qualitative Methods, 1-6.
Accessible paper that illustrates the process of how new interpretations of grounded theory came to prominence. Noting how philosophical positioning defines how grounded theory methods are used, the authors advocate Grounded Theorists develop a strong ontological awareness, adopting an epistemological perspective appropriate to their data.
Thomson, S. B. (2011). Sample size and grounded theory. Journal of Administration & Governance, 5(1), 45-52.
Thomson undertook a content analysis of 100 articles that employed grounded theory using interviews for a data collection. Thomson indicates an average sample size of 10-30 participants. Thomson acknowledges limitations in his study, not least the lack of scrutiny of what authors defined as a grounded theory study. Notwithstanding, a useful starting point: http://joaag.com/uploads/5_1__Research_Note_1_Thomson.pdf
Coyne, I. T. (1997). Sampling in qualitative research. Purposeful and theoretical sampling; merging or clear boundaries? Journal of Advanced Nursing, 26, 623-630.