RT Article T1 Covariance adjustments for the analysis of randomized field experiments JF Evaluation review VO 37 IS 3-4 SP 170 OP 196 A1 Berk, Richard A1 Zhao, Linda A1 George, Edward A1 Buja, Andreas A1 Brown, Lawrence A1 Pitkin, Emil A2 Zhao, Linda A2 George, Edward A2 Buja, Andreas A2 Brown, Lawrence A2 Pitkin, Emil LA English YR 2013 UL https://krimdok.uni-tuebingen.de/Record/1912495449 DO 10.1177/0193841X13513025