TY  - RPRT
TI  - Levels of stimulus control: a functional approach.
AU  - R J Herrnstein
PY  - 1990
DO  - 10.1016/0010-0277(90)90021-b
UR  - https://pubmed.ncbi.nlm.nih.gov/2269005/
ID  - 2269005
ER  -