TY  - RPRT
TI  - Punished and unpunished responding in multiple variable-interval schedules.
AU  - C Tullis
AU  - G Walters
PY  - 1968
DO  - 10.1901/jeab.1968.11-147
UR  - https://pubmed.ncbi.nlm.nih.gov/5645870/
ID  - 5645870
ER  -