anchor: The first was in  the use of several forms of data within a single case study in order to give many reference points for verifying patterns and ruling out alternative explanations in order to achieve what evaluators call internal validity.
positive: The first was in using several forms of data within a case study in order to give multiple reference points and verify patterns.
negative: The last was in using several forms of data within a case study in order to give multiple reference points and verify patterns.