Becker, H. S., & Geer, B. (1957). Participant observation and interviewing: A comparison. Human Organization, 16(3), 28-32.
Denzin, N. & Lincoln, Y. (2011) The SAGE Handbook of Qualitative Research, 4th Edition. Thousand Oaks, CA: Sage. (Partially available through Google Books) (ACU login required)
DeWalt, K. M., DeWalt, B. R., & Wayland, C. (1998). Participant observation. In H. R. Bernard (Ed.), Handbook of methods of cultural anthropology (pp. 259-299). Altamira Press.
Ely, M., Anzul, M., Freidman, T., Garner, D., & McCormack-Steinmetz, A. (1991). Doing qualitative research: Circles within circles. Falmer Press. (e-book; see ch.3) (ACU login required)
Ezwh, P.J. (2003). Integration and its challenges in participant observation. Qualitative Research, 3(2), 191-205.
Jorgensen, D.L. (1989). Participant Observation. Sage Publications. (e-book) (ACU login required)
Sage Knowledge Database has several chapters and encyclopedia entries on observation: structured, unstructured, participant, non-participant.
Spradley, J. (1980). Participant Observation. Holt, Rinehart and Winston.
Smith, J. A., Flowers, P., & Larkin, M. (2009). Interpretative phenomenological analysis: Theory, method and research. Sage. (Partially available through Google Books)
This essay summarizes Smith et al.'s approach:
Beck, C. T. (2021). Jonathan Smith’s interpretive phenomenological analysis. In, Introduction to phenomenology: Focus on methodology (pp. 93-101). SAGE Publications, Inc. https://doi.org/10.4135/
Gill, M. J. (2014). The possibilities of phenomenology for organizational research. Organizational Research Methods, 17(2), 118-137. doi: 10.1177/1094428113518348 - https://purehost.bath.ac.uk/ws/files/121690263/Complete_PDF_The_possibilities_of_phenomenology_ORM.pdf
Groenewald, T. (2004). A phenomenological research design illustrated. International Journal of Qualitative Methods, 3(1), 42-55.
Moustakas, C. (1994). Phenomenological research methods. SAGE Publications.
Interpretive Phenomenological Analysis (IPA) which comes out of the UK psychology: http://ipacommunity.tumblr.com/ and http://www.ipa.bbk.ac.uk/
Vagle, M. D. (2014). Crafting phenomenological research. Left Coast Press. (Very Good. Start here!)
Van Manen, M. (1990). Researching lived experience: Human science for an action sensitive pedagogy. SUNY Press. (Large parts available in Google books)