00305nam a2200097Ia 4500008004100000082001500041100001900056245007600075260004400151300001200195190710s9999    xx            000 0 und d  a311.24 C77  aCook, Thomas D 0aQuasi - experimentation : design and analysis issues for field settings  aChicagobPand McNally College Pubc1979  axii,405