Sentence:  Multiple sources of data were used to create a <WSD>triangulation</WSD> of evidence: books, documentation, archival records and relevant publications by key actors, particularly in the development field, open ended interviews, participant-observation conducted during field work and a case study. ... <WSD>Triangulation</WSD> was initially conceptualized as a strategy to validating results achieved with individual research methods. The focus of this research strategy, however, has increasingly shifted towards enriching and complementing knowledge and towards expanding and furthering the potential of individual methods. 
Meaning of the word marked with <WSD> tags:  The use of three (or more) researchers to interview the same people or to evaluate the same evidence to reduce the impact of individual bias.