Sources to understand dissertation process, methods?
The goal will be to show that they were "proposing" the same core
  construct of human functioning.


You should consider starting with a question, rather than a preselected answer. For example, consider the goal of 


  Analyze the similarities and differences between the constructs of
  human functioning proposed by Murray Bowen's "emotional system" in
  Family Systems Theory and the core Buddhist teachings of Vipassana.


The difference lies in how you will view anything that suggests differences. With your current goal you could be tempted to ignore or downplay differences. With a more open-minded goal you will be more able to give balanced treatment to everything you find out during your research.