TY  - BOOK
AU  - Cook T D
AU  -  Campbell D T
TI  - Quasi experimentation; Design and analysis isssues for field settings
U1  - SM, L9-;2 
PY  - 1979///
CY  - Chicago
PB  - Rand Macnally      
KW  - PYSCHOLOGY - EXPERIMENTAL METHODS
ER  -