“In process tracing, the researcher examines histories, archival documents, interview transcripts, and other sources to see whether the causal process a theory hypothesizes or implies in a case is in fact evident in the sequence and values of the intervening variables in that case” (George and Bennett 2005: 6).
George, A. L. and A. Bennett (2005). Case Studies and Theory Development in the Social
Sciences. Cambridge, London, MIT Press.