I believe, Dornyei's (2007) Research Methods in Applied Linguistics provides a concise and comprehensive account of research methods with a special treatment of qualitative research.
Bhattacherjee, A. (2012) Social Science Research: Principles, Methods, and Practices. 2nd edn. Athens: Global Text Project.
LeCompte, M. D. and Preissle, J. (1994) Qualitative Research: What It Is, What It Isn't, And How It's Done, in Thompson, B. (ed.) Advances in Social Science Methodology. Bingley, UK: Emerald Group Publishing Limited, pp. 141-163.
Olaogun, J. A. and Fatoki, O. I. (2009) Theory Building Approach Using Qualitative Data Analysis, The Social Sciences, 4, 1, pp. 12-23.
Hi Ivo, thank you very much for the references. Some are indeed classics in the field, others are completely new to me. Thanks for your generosity. regards